I think if your plan is to X/C you should just bet small yourself with plan to fold to a raise, that way you can set your price. If I were going to bet I would probably block bet for like 10bb and fold to a raise. I know you kind of open yourself up to some silly, " oh he bet small so he must be weak, I will raise" type stuff, but I just find they don't do that much, they just have it. You can balance it with some stuff that you will bet/call with. Something like QJ with a diamond. Blocks a lot of his value, or you can even do it with a 2 pair or a set. Or just not worry about it.

I think though that I might just X/F this river. You don't really beat anything he would value bet with, not when flop and turn are pretty big. Can't see what he has in the way of bluffs, other than some weird heart floats, which I don't think he would call many backdoor hearts on the flop when you bet so big. He shouldn't anyway. His FDs got there, his KJ and J8 got there, so he would have to turn a pair into a bluff,something like JT or J9. They are really good candidates to bluff with, both betting or raising, but not sure how many 5nlers turn pairs into bluffs.

chk/f river for me, easy game. don't be looking for villains to be calling down then bluffing rivers, aint gonna happen often enough and that river sucks.

Checking this river pretty much 100% of the time and deciding based on villains size if/when he bets. As played I fold to the raise.