I don't know about the first 2 but according to the training mode where you can see the damage points for each strike, it shows that leg kicks cause more damage points then body kicks.

sadly i also found out that BJ Penn's stiff "power jabs" that are supposedly the best in the biz are actually weaker than normal jabs... like the weakest strike in the game...

Leg kicks do actually make it harder to throw punches and kicks, i know this from experience. Also body kicks have been known to cause almost as much damage as a baseball bat getting smacked against your body.

i did leg kicks to a guy for a whole and every time he went for a take down i always got the sprawl so legs help get no taken down

i think that he's talkin about in the game lol

kicks to the legs are totally useless in the game, unless like u stated its to stop your opponents attack or setup a combo... they dont take off any stamina (i dont think, if they do its very little), and they definatly dont affect your opponents strikes/movements... kicks to the body will do damage, and can weaken the body up to setup a tko or even cause your opponent to get rocked, but be cautious and throw them with punch combos cuz all it takes from your opponent is a quick flick down on the right stick and you'll be on your back in guard