Are some of these two pair hands one pair on a paired flop? That would make a huge difference.

Two overs and NFD, or TPTK+NFD I'm generally willing to stack off. Do you have pokerstove so you can figure out why? I'm only folding these hands vs a nit.

Ugh. Think about this. It's a limped pot, so starting off there are 4-5bb tops in the pot. So you're going to standard stack off on a monotone flop with 99bb behind? What kind of hands would you expect villain to show up with?

All of your questions are really broad. There will likely be people posting very long responses. But any analysis comes down to ranges. What type of hands are your 2 pair up against, it could be a 26789 river, or a 29K flop. Those are totally different. DUCY?