I think this is a fold.
Villain probably does realize we should not have Jx and that for that reason, it seems like it should be a good bluffing spot and we should call.
The problem is that Villain can have a lot of Jx hands. Despite being pegged by Hero as good, he limp/called. Then he just check/called the flop, so I am guessing that we can de-weight combo draws in his range. His range is likely Jx, 9x, and maybe some medium-strength draws or smaller pocket pairs.
While this could be a bluff, it could also be a value hand, but I think there are two things that make this a fold for me:
1) Against this large an overbet, we don't actually need to call with all the 1 pair hands in our range. We should probably have Kx here a lot as well as AA and KK. So I don't want to throw QQ into our calling range here, on the off chance that somehow Villain had K
x
(or perhaps even K9) and passed us.
2) If Villain is good, he will know that the way we played this hand, the king hits our range--and he will also know that against a relatively unknown LLSNL Villain, which Hero is to him, it's really risky to try to bluff people off top pair, especially when they have a good kicker (as Hero might since he raised preflop) and it's only one more bet to get to showdown.
So it is worth asking, if Villain is a thinking player, and he is trying to bluff us, what hands is he trying to make us fold? Is he trying to make us fold Kx? If he is, we should call; but more likely his bet size is chosen to maximize value against a rivered pair that he thinks his opponent can't let go.
By the way, against a Villain that we are even considering calling here against, maybe we should have bet the turn?