since the flop is soaking wet and you virtually have the nuts you need to bet size so that you never have to make a hard decision on the river because there's like 99% chance that a scare card's gonna hit by then. a scare card hit and you have a hard decision on the river, that's why your bet sizing isn't good. as for what you should bet you should be able to do that math/logic yourself.

another factor here is that since villain is so tight you have to consider his range for continuing. he never has TPTK or something like that where you have to worry about keeping in the hand. his only hands that hit here are JJ+, 88, 76s-JTs and all sorts of combo draws and draws + overcards. every other hand is folding here REGARDLESS of our betsizing. and as far as the hands that are listed here: JJ+ isn't folding regardless of our bet sizing (except for maybe JJ, and POSSIBLY QQ) so long as you don't just push. 88 and all the hands with draws you want to make pay to continue and aren't totally upset if they fold. if the flop were K-high or somehting like that then we have to be more conservative with our bet sizing because we're trying to string along KQ, AK type hands, and depending on how dry the board is there are far less scare cards