#1 and #2:

Any turn that pairs the board is a bad barrel card. This is because regs generally check back 2nd and bottom pairs and so, without these in our range, we basically have some sort of fairly weak hand on average.

#3

c/r doesn't make that much sense. We never c/r a 6x here and 7x is very unlikely to c/r supposing we have one, which is again unlikely. We still rep some pocket pairs like 88 when we c/r the flop though, but on the turn we barrel we rule these out of our range also. So we basically have a draw. I would probably call off with 6x if I were in the small blind since all the draws missed.

#4 I'd check back the flop since any pair with a club has 50% vs our hand and since we lose to Qx. On the turn, your bet is too big. You want him to call with 6x etc so i'd bet half pot and jam rivers that aren't clubs.

#5 Flat and check-jam any turn, expect possibly an ace. You should be trapping on the flop.