If you can provide additional readings on these topics, especially researches/full books that would be great
1: The composition of a fort wall, let's take fort Ticonderoga for example
https://en.wikipedia.org/wiki/Fort_Ticonderoga#Construction
The walls were seven feet (2.1 meters) high and fourteen feet (4.3 meters) thick ... they were made of squared wooden timbers, with earth filling the gap. The French then began to dress the walls with stone...
Not limiting to fort Ticonderoga, but for all the Bastion Forts in that era, what's the typical stone:earth ratio of these walls are? What types of stones were typically used
2: How effective are these forts against siege weapons? Where there effective ways to destroy the walls directly?
From what I understand, in that period, field artillery uses solid shots, which are probably not effective against thick walls like these. "Siege artillery" like mortars fires larger shells. Made of cast iron, filled with black powder. I have only seen modern shell vs concrete fortification stuff, but haven't found any data on how well do black powder shells do against the walls, if any of you have materials on this, please share
3: I read that these forts were pretty effective against direct assault, usually it takes the invading force many times more people to attack it with infantry. Or it takes long sieges/long term bombardment of the fort. Has there been any incidents that a fort is directly destroyed/heavily damaged in a frontal attack?
Much more earth than stone, generally- consider how these bastion forts, or trace italienne, are designed. You have a low, sloped wall, with a ditch in front of it. Medieval curtain walls relied on mortared stone to stay upright, thus providing their main advantage- an elevated fighting platform. But once cannons started to be used in large numbers during sieges (end of fifteenth century, particularly Charles VIII's campaigns in Italy and Ferdinand & Isabella's war against Granada) the curtain walls proved quite easy to knock down. If you hit the base enough times, the gravity of the rest of structure brings it down. Early modern bastions don't need nearly as much stone to stay in place, as they are essentially constructed earthen ridges. The stone or brick on the fortifications keeps that earth where it is supposed to be (protects against the earthworks eroding into the ditch) and gives a stable and protected platform from which to fire at the besiegers. You might be able to break up some of that wall with cannons, but you can't really do much damage to the sloping earthen wall, any more than you can destroy a hill. So even if there's a breach, there's still a (literal) uphill battle ahead to take the fort.
Modern artillery, as OP notes, could do serious damage to a bastion fort. They did eventually become obsolete, after all! But this was not until the 19th century, with the advent of high explosives and industrialized warfare. Early modern mortars (and various forms of shell shot, meant to explode in the air above the foe) could certainly cause damage to individuals and weaker structures inside of fortifications, but were not particularly effective at destroying the walls themselves, as they were still relying on black powder.
Geoffrey Parker's The Army of Flanders and the Spanish Road 1567-1659 has some data to shed some light on how these fortifications fared in action, against one of the best armies of the age. 95 Dutch towns were captured by Spanish forces between 1578-1590 during the Eighty Years' War, 60 of which were taken through direct military action (the rest were mostly undefended or fell through surprise or bribery of the defenders). Half of those 60 captured towns had at least some modern trace italienne fortifications, the other half did not, relying on older fortifications if they had any. The towns without bastion walls fell either by storm (8) or by surrendering once the artillery arrived (22) but before they were fired upon. The defenders understood that medieval walls were indefensible against the Spanish artillery train. In contrast, out of the 30 properly defended (but still captured) towns, only one was taken by storm (Maastricht in 1579)- the others surrendered, many after several months of siege, due to being cut off from supplies, and without hope for relief. On the other hand, Mons, Leiden, and Haarlem (to give a few examples from just the 1570s) all withstood months of sieges and ultimately outlasted the besiegers. So yes, although it is possible to storm a bastion fort, early modern commanders understood that to do so would be incredibly costly and would likely not even succeed. Despite being outnumbered about 20-1 in soldiers, Maastricht took four months of bombardment and defended against two assaults (causing thousands of casualties before finally being taken in a nighttime attack and brutally sacked. Of course, the fear of being sacked itself was perhaps the most effective weapon against fortified towns, as such treatment became increasingly likely as sieges wore on and deaths mounted among the besieging army.
To Parker, this evolution in fortification brought on the massive increases in army sizes starting in the sixteenth century, and it is certainly true that wars of sieges necessitated larger and more permanent armies than wars that could be decided by a pitched battle. I don't know that this by itself caused the expansion of armies as much as the increased centralization of early modern fiscal-military states allowed for the creation of larger armies, but it is something to consider.