You can see your AP stats in the char screen, but to sum it up:
Your max AP is 7+CON+2 if Lone Wolf. With a base of 5 CON, that means your max is 12 or 14 with Lone Wolf.
Your per turn AP is 3.5 + (SPD/2) + 2 for Lone Wolf, rounded down. The tooltip on that is confusing it shows base as 4 instead but you only get +1 when you get an odd number of speed, so 7/9/11 etc. Anyway with base SPD of 5 that's 6 or 8 with Lone Wolf.
Glass Cannon just multiplies that by 2, so that's 12 or 16. In short, unless you have Lone Wolf or have more speed than constitution(which you shouldn't if you go glass cannon), you won't be capped. Even if you do get more than you can hold, it's still worth it because going from 6-8 per turn to 12 is a huge difference(and for Lone Wolf it's even better), and it'll increase once you start finding good items with CON or when you're done maxing your main stat, they cap at 15 so at some point you'll have to invest in other stuff, unless you hybrid then you don't have spare points.
As for the sneak discussion, the point of getting Sneak up is if you play a rogue character. Guerilla does double damage when you attack from Sneak, having Sneak at 5 makes it cost only 1 AP, so 3AP to sneak+attack with daggers and do double damage, it's very strong. To get 5 asap, start with 2(remove points from stuff or just do it on level 2), get the Cautious trait from Fabulous Five recruiter guy or somewhere else and get boots/helm with +sneak, mostly check the captain of the ship and the rogue/witchcraft vendors, make sure to save before you check their inventories, then check, if they don't have anything, reload. Find one on each to make it easier as finding both items on the same vendor is rough. Vendor inventory is generated whenever it's opened(pickpocket or vendor window) and resets every level. If you want specific spells and stuff make sure to save before you check a vendor so you can reload if they don't stock it. A bunch of spells are unique static drops in the world or are only made from scrolls with Crafting though.