Got a few technical questions regarding how we should build our preflop ranges when we play HU 100bb deep with 0.5BB ante.
First of all I think BTN should open his whole range, given the fact that there's so much money in the pot already.

Let's say BTN uses 3.5X as a standard open, that means his required equity should be 37.5%, the same as he would need to open 2X in a regular game.
From BB's perspective, he'd have to put 2.5BB for a total pot of 8BB, so he's required equity is 31.25%, the same as he'd need when faced a 2.7X open in a regular game.

My main questions are if BB should play his range accordingly to vs a 2.7X open in regular game or maybe go even wider than that, given the fact that BTN's range contains 100% of hands so he's gonna fold a lot agains 3bets? And if that's the case, should BTN now adjust by 4betting lighter or he should stop opening the bottom 10% of hands even though that are most likely +EV to open? Or maybe implement a complex limp strategy?

What other adjustments should be made in this game also given the fact that stacks play shorter?