As a very active participant in The Island, I think I can explain a few things...
1. Every action drains your own stamina, same goes for your opponent. The only action that drains your opponent's stamina is tickling her.
2. The entire goal of The Island is to max out your opponent's lust, raising your own is counterintuitive. I'm unsure about the futa thing, as that's not one of my personal kinks.
3. Technically you're helping them, as you weren't there when they started to fight, so it makes some sense that only they would get a point.
4. I believe the difference between the two takedowns is the direction you're facing (torso/legs) rather than if she's lying face-down or up. For her to be face-up, take her down from neutral. For face-down, takedown from behind.
I hope this helps clear things up a little bit, but if I'm completely wrong and all of these things are bugs... I won't be surprised at all.
Have fun!