PLO25 AA65ss postflop, rep FH on river?

Why isn't calling an option for you?

Losing to all value hands and flop being rainbow decrease those bluff combos? Though probably would need to get some small full houses to fold to bluff either.

If you had 99, would your line be half a pot on the flop and check turn?

The thing on the river raise is that in general players don't like to fold straights there. And if your line looks suspicious, opponent is more likely to call. With a big raise, your bluff needs to work quite often.

your bluffraise idea of having blocked most of the boats is good, unfortunately you should bet 99/66 on turn so this is a simple giveup.

with bdfd and bottom2 plus no straightblocker i check behind btw. i just say this because you should NOT start to 2nd barrel turn in future