Before I move on to answer your first question, I'm going to have to disregard your last point: Thomas Gage was not intending to disarm the Lexington and Concord militia, something that would indeed have been illegal and would have taking their private property. The goal of the Concord expedition was to seize and destroy gun powder, musket balls, cannons and small arms as well as provisions being stored for potential military action by the Provincial Army of Massachusetts against the Crown. This was a different matter altogether and in General Gage's original instructions, he mentions quite clearly that "[b]ut you will take care that the soldiers do not plunder the inhabitants, or hurt private property."

It's difficult to generalize on how an argument such as yours would have been considered by an average American colonist. So, to answer your question, I will do so out of the perspective of a Patriot/Whig Bostonian.

Your argument:

I think it was reasonable for the Ministry to tax the colonies to pay for the enormous debts Britain ran up in the Seven Years War and to protect those colonies. I accept the Declaratory Act's power to tax or regulate or legislate for the colonies in all cases whatsoever. I view the whole "no taxation without representation" argument as spurious.

At the end of the French and Indian War, Boston finds itself in dire straits. The end of the war has left the colony of Massachusetts in heavy debt which resulted in the inhabitants of Boston having to endure a 60 % increase in provincial and town taxes. The economy of Massachusetts, just like in many other colonies, suffered a depression which was only made worse by the lack of jobs now that the war was over. Many men were unemployed and the influx of men who had been released from military service only increased the competition between them. Established businesses failed due to the financial hardships and the poor in Boston became more than they had been before. Those that suffered the most were probably the women and children left behind by men who had died in the war. Poor relief increased year after year, adding an additional burden to an already worrying economic situation for the government of Massachusetts. To this already bleak picture, Boston is also ravaged by a fire (afterwards known as the Great Boston fire of 1760) which results in more than 200 families being homeless and countless of houses and warehouses being destroyed. Furthermore, Boston also suffers a smallpox epidimic that ravages the town.

Now, after reading all of that, you now have to put yourself in the seat of someone who hears that Parliament has suddenly decided to levy a tax on you for the purpose of raising revenue. Not only are you barely able to pay the taxes that your representatives (if you are male and fulfill the requirements of being able to vote) have in your eyes lawfully levied on the population of Massachusetts, but you now find yourself having to raise revenue for troops that you see no point should be raised in peace time. If you're a merchant, you now how to pay taxes not to regulate trade but to raise revenue. To add insult to injury, the Parliament does this through intruding on your rights as an Englishman. After all, Bostonians considered themselves Englishmen with all the written and unwritten laws and rights that came with it. Parliament could not tax Massachusetts without proper representation, as per the "natural rights" of Englishmen.

From this arises the argument that "taxation without representation is tyranny". If Parliament can suddenly decide to treat you as less than an Englishman and revoke one right, why can't it revoke all of them? Although the Sugar Act of 1764 might only affect merchants, the Stamp Act of 1765 and the Townshend Acts of 1767 affects the entire population of Boston. This makes people angry and it makes them act. From the lowest to the richest; men, women and children all join in protesting against the acts. Even more individuals are pushed to the patriot camp during the occupation of Boston by British troops between 1768 and 1770, with the ensuing tensions between the citizens of Boston and the British troops culminating in the Boston Massacre on March 5, 1770. Although the troops leave after this fact, and the Townshend Acts are revoked (except for the tax on tea), this all flairs up again in 1772 when Parliament decides that the revenue raised from taxes in the colonies would pay for the salaries of certain civil officials, like the governor and judges, (which is otherwise paid by provincial taxes), which removes the power that the electorate would have had over them and in their opinion making them more accessible for corruption. This is followed by the 1773 Tea Act which once more has a direct impact on the citizens of Boston. This in turns leads to the Boston Tea Party which leads to your next argument:

I think it was unwise but not ultra vires of Parliament to suspend the government of Massachusetts in 1774.

The provincial government of Massachusetts was quite autonomous. They considered this their independence. The Parliament didn't suspend the government of Massachusetts; they revoked its 1689 charter which changed its entire government form and made key positions in the Massachusetts government ineligible for election by representatives voted by the people. Furthermore, it also limited the amount of town meetings to once or twice a year as well as having to have the agenda of the meeting approved by the governor before the meeting was held. The Massachusetts Government Act thus disenfranchised the entire colony of Massachusetts which put rural Massachusetts on fire; although rural Massachusetts had thus far felt unaffected by Parliament's taxation, they suddenly found themselves having their rights as Englishmen being taken away from them. Worcester is an excellent example of this. 90 % of Worcester's male population were enfranchised. Now, out of nowhere, they weren't. By the end of 1774, towns all over Massachusetts from Springfield to Plymouth to Worcester had shut down the county courts and effectively overthrown British rule. Only Boston remained under British control by December 1774 due to its occupation.

Adding on to this, you have a series of additional acts pushed upon Boston as a collective punishment for the Boston Tea Party: The Boston Port Act shuts down the entire port of Boston for commerce until damages has been paid to the East India Company. Administration of Justice Act (famously known as the 'Murder Act') meant that Crown officials, such as customs agents, could get a trial in England instead of Massachusetts. This was believed by Patriots/Whigs to make it possible for Crown officials to get away with murder.

All of these factors leads to not only the Suffolk Resolves which deems the Coercive Acts to be unconstitutional and to essentially prepare for a possible war if they were forcefully enforced on the population of Massachusetts, but also to the decision to nip the rebellion in the bud by sending 700 British troops under Colonel Smith to Concord to destroy military supplies gathered by the Provincial Congress. Gage had already successfully done so in the autumn of 1774 but had failed in both Salem and Portsmouth, New Hampshire. He would fail again on April 19, 1775 and trigger the Revolutionary War.

This is at best a small overview of all the issues happening in Boston (and after 1772, wider Massachusetts) during the decade leading up to the shots in Lexington. Things I haven't mentioned here, like the writs of assistance, the impressment of sailors into the Royal Navy, the importance of newspapers and political pamphlets, political clubs/organizations and the deeper effects of the occupation of Boston in which men had to compete with British soldiers for jobs and other issues, were all parts of what made some people into Patriots/Whigs and support the resistance against the overreach of the Parliament.

If we go by your arguments, we can assume that you would probably not have been a Patriot/Whig in Boston. You wouldn't have been alone in this matter and you would have found plenty who agreed with you. Not everyone agreed with the resistance against Parliament, many did consider it the right of Parliament to tax the colonists and some considered the violent protests that sometimes flared up in Boston in response to the acts of Parliament to go beyond acceptable. Yet to fully understand why the American Revolution happened as it did in Boston, we have to go down to the grassroots and go beyond simple politics, acts and rights. We have to look at certain sections of society and ask why this or that person supported this or that side. You will not get one answer to cover them all. A shoemaker is not going to be motivated by the same reasons as a merchant, but their thoughts and motivations might overlap. Context, in my opinion, is vital to the understanding of revolutionary Boston.

Sources and recommended reading:

The Glorious Cause: The American Revolution, 1763-1789 by Robert Middlekauff (Oxford University Press, 2007).

As If an Enemy's Country: The British Occupation of Boston and the Origins of Revolution by Richard Archer (Oxford University Press, 2012).

The Minutemen and Their World by Robert A. Gross (Hill and Wang, 2001).

The First American Revolution: Before Lexington and Concord by Ray Raphael (The New Press, 2011).

Defiance of the Patriots: The Boston Tea Party & the Making of America by Benjamin L. Carp (Yale University Press, 2011).

The Shoemaker and the Tea Party: Memory and the American Revolution by Alfred F. Young (Beacon Press, 2000).

Paul Revere's Ride by David Hackett Fischer (Oxford University Press, 1995).

The Boston Massacre by Hiller B. Zobel (W. W. Norton & Company, 1996).