I don't mind a fold here, there is def hands like J3/QJ/83/J8 in his range and fish will sometimes take this line w AK type hands too. Yeah, he could have a busted draw, but fish will more often flat or fold any kind of SD value here, even Kxcc/Kxss. You need to be good 33% of the time here and you need him to check a ton of draws on flop to have that much equity here
Yeah, I think it is too tough to find a 34% bluffing range here. I fold as well. Fluhsdraws should bet more on the flop and there should not be that many poeple who will bluff the river that way imo