1) If I sneak into a town at night and strangle/bash the crap out of people while there sleeping, will it make the town hostile to me?
Yes, town guards are psychic. In fact, all civs are psychic. You do one wrong to anybody in the civ and you're DOA.
2) How deadly is throwing?
Extremely deadly, particularly with coins. Then again, so is sand and vomit, so, in short; very.
3) Sneaking, when do they notice you?
Depends, they generally only notice you if you are within melee striking distance, so right next to them, but there are a few outliers where low skill sneak users will be spotted at range. Throwing while sneaking CAN work, but, it has it's limitations: If the target is laying down or not an enemy (i.e. humans you haven't attacked yet) you can't throw at them until you actually get a melee off then REsneak. However, the REAL value (to me) of sneaking is the resneak. Attack something, then run off, go around a tree, sneak, then back off and let them look around confused.
4) Wrestling, how does it work?
If you grab someone's clothing, weapon, or shield, you can TAKE it from them. Once you have a grab on it, hit shift-i, scroll down (the text will be red) and you'll see their item in your screen. Hit it's letter and it will ask if you want to gain possession, then you will have the regular skill-check to see if it works.
Joint locks can be strange, for some reason you can't do joint locks and breaks on certain creatures (usually 4 legged) but that MAY depend on your wrestling skill.
Strangling and eye gouging are easy and fun! About eye gouging, the previous commenter said grab the "face", you actually want to grab the head, but, that's semantics, as long as you grab with your hand, and make sure nothing is already in your hand, then you will have the option to gouge.
Best of luck mate, you're gonna need it =)