villain looks like a solid regular, rather on the tighter side playing 19/15/4 over 63 hands

until here should be standard, i have way more flushes and 6x than he does at this point, so i elect a big sizing

river gets tricky, on the one hand there is still some value to be had, but i was also kind of afraid that he would raise me with the Ks/As blocker, which is probably a large part of his range. but i also have for whatever reason the bad habit of always taking into account the worst case scenario, rather than the best case, which is why a lot of my lines at one point get passive. do you bet river and if yes, what sizing do you use?