Hand 1. This board is a pretty bad place to barrel 3rd pair given his likely PFR range from the SB. And with a 40bb stack, this is a pretty bad line.

Hand 2. Don't limp preflop. As played, shove the river. This is value town.

Hand 3. 3betting w/ JJ and a 40bb stack is very dicey. This hand plays great for a call even multiway when you're 100bb deep. As played, sure, shoving the flop is fine with only $2 behind.

If you're gonna play a 40bb short stack, you need to learn something about how that changes the game. Hands like T7s need deeper stacks to show profit.

I suggest buying in full (100bb) and learning more about ABC Tagg poker. Short stacking isn't hard, but it requires an understanding of some theory that you don't seem to have.

Good luck.