Hi
Make more squads with less dwarves. 2-3 Dwarves squads spar more and thereby get better sooner.
Let them train around the clock. Give them good bedroom near the barracks and try to cook some roast for the happy thoughts.
Those guys always want the best of the best, so when you produce a slightly better iron helmet, they drop theirs where they stand and get a new one.
A) Nothing, You can try to burrow them but really "forcing" them is not possible. It will take some time for them to get all their equip, but they gonna get it eventually. Of course they sometimes wear the bootes on their hands.....
B) "v" "i" I think to look at the inventory of a dwarf. Or in military screen under equipment and then I think it was "P" to look at the equip a military dwarf is wearing.
C) Random stuff

No way to choose, but with smaller squads with similar lvl of skill they spar more often, which I think is the best way for them to train.
2) They claiming those items for themselves. You can try to take them away, but they probably just take it again. And yeah they are kinda "stealing" those things.