1. I've been under the impression clothing quality only affects value, but clothing material does (with bear fur being the best fur material, if I remember correctly). Note that this is far from a confirmation of any kind.
2. Bear skull/teeth: as MrMotorhead said. There is a use for bear teeth as well...
- Bones: dogs can eat them, but I've found it's a pain as the mutt barks every time it nibbles at a bone, and it isn't really sufficient to keep it fed. Dogs eat bones of the same type in a round robin fashion, so you'll end up with a lot of partially eaten single bones if you try to stack everything into one pile. Also note that human corpses decay into bones as well, and dogs eat those too, without being starved. Thus, I pile the bones of slain foes in a big pile on a rock in the rapids my character's homestead is located by.
Interestingly, the bones from different humans do not stack; Njerps, Reemi, and Vagabond robbers form 3 stacks.
- Antlers: I've found no use for them beyond being a source of mod reactions (such as e.g. Buiodda's Crafting, which also uses bone and bear teeth).