Imagine this hypothetical situation: You are HU in the end of the sng, and you both have 10xBB. (Sng at Party, blinds 200/400, both players have 4000 chips).

1) Is it +EV to push every hand from the SB ? If not, what hands are +EV to push?

2) If your opponent pushes every hand from his SB, what calling range is +EV?
What if he pushes 75% of his hands?
What if he only pushes only 50% of his hands?