I always feel a bit lost in this situation, but I usually end up calling, unless against a very passive player.

Looking at hand 1:

First of all, if we are behind on the turn, more combination he might start with gives him two pairs
(86,89,96,j9,j8,j6) than a made straight. (7T, TQ). (His range is pretty wide, completing in the SB)

If behind two-pairs with a J, we have
4 outs to the straight
3 outs to to two pair

If against two pairs without a J , we also have
2 outs to JJJ
3 hidden outs.

When against two pairs with a Jack, we have
7 outs (Q and T)

When against a made straight, we have 4 outs, but might split.

When against a smaller set, we have 7 outs (J and T)

Not considering implied odds, we need clean 8 outs to call if we are always behind, getting 1:5. If we are ahead a semibluff even a third of the time, I guess we need only 5-6 outs when behind to call, which I do think we have on average.

My thinking may be flawed, maybe the implied odds make the difference and we should fold, since we will often pay one more bet on the river when behind, and might not make up for it when ahead on the river?

As I see it you have to be fairly sure that he would very rarely semibluff in order to fold here, due to the outs you have when behind.

Please comment on this, I am nowhere near sure that I am not overlooking something.