it's a poor decision to not buy-in full for numerous reasons at microstakes, for one you lose a lot of value from poor players, but also the rake as a % of the pot is fairly ridiculous and you have to have quite a large equity edge/winrate to overcome it. 50bb stacking it makes that pretty difficult.

As for the hands

1. shove turn
2. I'd bet flop, we have a lot of equity when called, as played river seems like a good value bet but I'm not expecting to be good here when called every time, but enough.
3. 4bb it UTG, turn shove is ok, we're committed regardless
4. 3bet PF, fail that, just call flop and use our position to our advantage