I will answer all questions at once because there was a lot of wrong answers.
ranged ammo is basicy a mini spear in hand to hand that lacks a crit boost.
Ranged ammo has a hardcoded critboost (I think it's 2).
- How do I twist stuck-in objects?
Shift-A (wrestling) -> grab it, attack (another hand should have a shield or no weapon)
Shift-I to maintain possession
- How do I specifically gain strength and toughness, rather than agility?
All yous stats level up randomly when you get XP.
- Does it actually do my companions any harm to be constantly hit with wolves and cougars and alligators hurled by my hammer?
No
- Just how tough do I need to BE to take on an elven forest retreat?
You need a high shield skill, that's all. And have some shields, not one. No toughness can save you from a well-placed arrow in your head.
- Is there any way to find caves that doesen't involve questing?
Worldgen options. Caves visible -> yes
though I apparently wasn't strong enough to pull it out
You mean to Shift-I? This way you pull items out of alive creatures.
About GCS specifically, but otherwise general hints are good too.
If your speed is >1000 and you have revealed a GCS, there's nothing to fear except for a well-placed web. Run around and shoot/throw things. Don't let it web you by keeping a distance and hiding behind trees/obstacles.
Also, axes and swords are the best because the more limbs you hack off, the easier it's to attack the body. Don't use spears because it feels no pain and hammers are bad because they require a luck to hit vital bodyparts and don't cause any bleeding.
- What's the best item for throwing? I have some masterwork steel bolts, a few rocks, and a handful of live flies.
Any piercing weapon, like ammunition or spears. Because they has a very high chance to damage vital organs.
- What's a good speed, and how much crap can I lug around before I reach too low?
>1000
animal joints
Any consistent mod has it.