Contrary to its depictions in pop culture, the etiquette of the Victorian era was not a terrifying maze of minute changes in protocol for every gradation of acquaintance or rank, so this is actually a rather simple question. You've already gotten the rundown on aristocratic titles, which can conform more to the stereotype of unnecessary complication; these were, of course, reserved for a very small group of British people during this time - Americans obviously only had titles if they married in. I'm guessing from your question about suffixes that you might be familiar with the Japanese -chan, -kun, -tan, etc.? This type of system was not present in either American or British English.

Etiquette books were aimed at the middle class and upper middle class, to help them separate themselves from the lower middle and working classes with noticeably "refined" behavior, and so they give us some insight into both sides of the equation. One of the things that all etiquette books of the period covered was the subject of introductions. Gems of Deportment and Hints of Etiquette (1881) is fairly explicit about why introductions were important in middle-class society:

For beneath the few formal words which are a mere announcement of names and position, is a deeper meaning conveyed through the social ceremony. The formula of expression may be simply, "Mr Smith, allow me to introduce to you my friend, Mr Brown," but the unspoken words will be, "he is my friend; as such, you can trust him, take him into your home, introduce him to your dearest and best; I am responsible for his good behavior. Open your home and your heart to him on my tacit recommendation of his good qualities; I am his social indorser." As people are not required to show a diploma of good conduct before they can enter the social arena, as doctors of medicine must bring their testimonials before their brethren recognize them, so many an impostor creeps into the social ranks, bringing rout and confusion with him. Therefore it is wise to know who Mr Brown is before you introduce him to your friends ...

If you were seen to be familiar with someone, it was assumed that you were endorsing them as Good Society; therefore, if that person were Not Good Society, it would reflect poorly on yourself for mixing with them - both because you might also be Not Good Society if you enjoyed their company, and because you might have opened other people up to this Not Good Society. As a result, the people who cared about Good and Not Good Society limited social contact with strangers, and once they were formally introduced and known as Mr./Mrs./Miss [Lastname], there was a certain social weight to their acquaintance. (There were exceptions to the need for direct introductions; for instance, people staying at resort hotels could socialize casually. However, the flipside of this freedom was that once you returned home, you couldn't presume on that acquaintance - because it lacked the social endorsement of the formal introduction, neither of you were guaranteed Good Society.)

Special note for Mr. and Miss - in some families, there would obviously be multiple Mr. Smiths or Misses Jones. In these cases, the eldest one would be known as Mr. Smith or Miss Jones, and the sons/younger brothers and younger sisters would be introduced and discussed in the third person as Mr. James Smith, Mr. Robert Smith, Miss Elizabeth Jones, and Miss Mary Jones. They would still be addressed directly as Mr. Smith and Miss Jones.

The use of first names (often referred to as "Christian names") and nicknames ("pet names") was restricted to people who were very close to each other - relatives and intimate friends of the same gender. Schoolgirls would call each other by their first names irrespective of the level of friendship between them, but once they left school they were supposed to be Miss Lastname unless they were close. Eliza Lavin's Good Manners (1888) recommended that young women not use first names unless they were very close, because if they had a fight or things just went cool between two of them, it might be awkward to make what happened clear to everyone else by changing back to a more formal form of address. As a former young woman, I can definitely imagine!

Relations between husbands in wives in private were not in the scope of conduct manuals in general, since their focus was on how society perceived you, but they would sometimes discuss how they should behave in public - they shouldn't refer to each other by their first names unless the spouse and whomever they were talking to were also very close, and should instead use Mr. and Mrs.

There were common courtesies in England and the US that remained standard; however, England has the distinction of having titles. Which, to the modern man can be incredibly murky and confusing.

In England during this time period, you had royalty, aristocracy, and commoners.

Queen Victoria would have been addressed as “Your Majesty” and then, depending on level of intimacy, as “ma’am” thereafter.

Her children were highnesses. For example, her eldest son, Albert Edward “Bertie” (later Edward VII) would have been addressed as/referred to as Your Royal Highness/His Royal Highness (HRH); and as “Sir” to close friends. His wife, Alexandra was also an HRH and would have been referred to as such and then as “ma’am” thereafter.

Aristocrats (which included: Dukes/Duchesses, Marquesses, Earls, Viscounts, Barons, and Knights) have varying titles according to rank.

Dukes and their spouses were referred to as “your grace” when addressed. However close friends could refer to them simply as “Duke” or “Duchess”

Ex: “nice weather we’re having today, eh, Duke?”

Marquesses on down were Lord and Lady “such and such”. Servants referred to them as “your lord-/ladyship”

Dukes, Marquesses, and some earls had the “of” distinction to their titles. Ex: Duke of Norfolk, Earl of Sandwich. However some earls did not have an “of.” Ex: Earl Carrollton. I am unsure if there is a distinction between having an “of” or not.

I believe all Viscount titles had no “of” as it is usually a subsidiary title (the eldest son of an Earl [if the Earl had a subsidiary title] would use his father’s Viscount title). If a title holder did not have a secondary title, his eldest son would be referred, for example, to as Lord George Walters. This is a courtesy title. The sons of title holders use their father’s legal last name, not the title name. Lord George Walters’ father could be the Earl of Sandwich but George would not be referred to as Lord George Sandwich.

The courtesy title of Lord was only for the sons of Dukes, Marquesses, and the first son of an Earl. The second and third sons of an Earl were “honourables.” The same is true for daughters but all the daughters of an Earl are referred to as “Lady [first name] [last name]”

The title of Baron was hardly ever used directly, it was moreso a classification. Barons were referred to as “Sir [first] [last]” and their wives as “Lady [first] [last].” Their children were simple “Mr.” “Mrs.”

The Victorian era was very formal outwardly. After you got out of titles the Mr/Mrs classifications as standard. It would not be strange to hear a husband refer to his wife as “Mrs. Brown” when she is in the same room as him.

The same was typically true of America in spite of political titles (which were not hereditary). The Mr/Mrs was standard. It’s not so common today, but in those days wives referred to by their husbands names, ex: “Mrs. William K. Vanderbilt” not “Mrs Alva Vanderbilt” —at least officially (party invitation) at the actual it would just be “Mrs. Vanderbilt”

Hope that helps. I’m a little rusty.

Edit: as far as nicknames, they were very common. Queen Victoria’s eldest daughter, Victoria, was almost exclusively referred to as “Vicky” by her parents/siblings/some very close cousins. Formality was strictly enforced but amongst family, nicknames were common.

Queen Alexandra: Alix Edward VII: Bertie Victoria Louise: Ducky

Very close friends would use first names in private. Not in public.

Correction: the wives of Barons were referred to as “Lady [last name]”

So, Laura Fillsey’s husband is the Baron Fillsey. He would be referred to as Sir Edwin Fillsey and she would be Lady Fillsey.