I would say the preflopdecision should also depend on SB a bit. So i would rather flat if im last to act before the fish. But if SB is nitty this call is fine.
Im usually not tempted to bluff into 2 guys with 1 of them beeing a fish as i expect FE to be too low in this spot. We could also consider start bluffing favorable turns as we usually get credit on later streets in MW-pots as well when we show aggression (we simply check a lot of marginal but not too weak hands OTF).
Therefore my approach would be to bet pretty polar, i would not choose this sizing (I dont use it at all in MW-pots) and would be betting more like 50% here.

3b or fold pre would be my play but I think charts are going to mix this. Again, they are usually designed for stakes where rake is less of a problem. If I had to call pre, I would like KTs/KJs since it's harder for him to have something when we flop a straight (KTs on QJ9 or KJ on QT9 is better for us than QJT with K9s). CO is uncapped. Yes, we do block AK but he still does have 12 combos of it in has range here for sure.

3 way, I am probably just done with the hand on the flop. Would bet more heads up.

As played, if we are betting river, I think it will be bigger. Boats, straights we back into (76s, 65s, T9s, 5x) are going to want to bet big (not to say your big isn't fairly big). We do hold the blocker to T9 which is kind of nice. We do have quite a bit of value we walked into here so bluffing here some some 9x/Tx will be fine. I think we choose a big size with our fat value so I would choose a big size with out bluffs with good removal. We can potentially size down with some of our thinner value bets (8x/99/TT).

Id take the sdv on river
Rest I like nice hand

What value hands take this line? The only ones that make total sense to me is 45s and 66, pocket 55, A5s(3 of 4 diamonds barrel). Other possibilities only you can answer, Do you check back 87s, 56s, 77, A8, 88 on the turn? Do you check back 9Ts on the turn?

So 3 combo's of 45 and 66,6 combos of 55, and 3 combos of A5 for 15 combos of value hands for sure take this line.
So you need 15 bluffs K9 seems like a good one to me as K9s would be ideal as it blocks a 9T combo. QTs for 4 more combo's, JTs, with your k9 suited, and J9s. Seem like a good bluff range to me.
Be mindful that this is still likely not enough bluffs cause diamonds combos of those hands probably double barrel and some of your other value hands you may slow play on the turn I don't know your game to know. More often players tend to slow play the flop and not the turn.

Once you fully understand your value range you can design a good bluffing range that is balanced. Then you can figure out in your game if this spot is over or under called in your games and design an exploit around what your data says about this spot.

I think K9s is gonna be one of the better bluffing hands in your range with little sdv so seems like a good bluff to me.

I don't even know why you guys bother with these crazy bluff lines. It's not even necessary in today's games. All that winners do is value up, put in insane volume, and subsidize their winnings with coaching profits, writing articles, etc.

It's just a matter of insane volume.