Both are probably bet/folds on the flop.

Hand 1 - this is a pretty drawy board. You are cbetting into 2 villains on a drawy board. A competent player probably isn't going to be c/raising with a player left to act light here. So a reasonable assumption would be that we are likely behind his value check/raising range. That is, I don't think he raises many worse hands for value (A9, etc). However, this is pretty dependent on the player and his view of relative hand strength.

Also, given the action he probably isn't bluffing often, if at all. So you can probably safely fold the flop.

As played, fold the turn. You never have a 6x hand in your range (other than 66), whereas he can have 76, 65, 66 for the straight. You likely don't open JTs from UTG, whereas he could def call preflop with it. He can still be valuebetting sets, whereas you probably get them allin on the flop. So in essence, his range is much stronger than your range, and I highly doubt he is bluffing here. So fold.

Hand 2 - Also probably a bet/fold on the flop.