So, on the river you just fold it imo. You just get there with so much better stuff that you don't need to call any pair probably. If you call the Turn with all middle pair + gutshot and raise flushes after raising 2pair + on the flop you'll get to that river with 55% of range being 2 pair + and if you are to call pairs you'd much rather have a Q or an overpair. So when you see it you have JJ, KK and Qx around 25% of the so that makes for 80% of the range being better to call that KTo.

Flop seems a clear call.

Now turn is the interesting one. It will come down to how you play the flop I guess. Think that if OTF you raise a decent amount of Ax of hearts and overpair+ it's a call OTT but if you decide to go with a call only strategy OTF it becomes very close. When you think that he as a T or the flush think it becomes a fold.

It depends a lot on that flop strategy because when you raise those strong hands the KT becomes higher in your range so you'll need to call it more but if you don't it will go down and are more confortable folding. (I know you already know this and anyone that reads this also does (probably), but can't hurt to write ig)

Honestly, I don't like calling the river on any card that doesn't improve it, KT is kinda bottom of range that calls turn and if it doesn't improve it's garbage now. Unless villain bluffs way way way too much I'm folding it on any non K or T.

i did end up folding but i would have stuck around to see showdown if the 4th heart didn't land. Are there any river cards that would be a good spot to bluff raise?

Calling 'hoping' he doesn't fire is no good. Make a note and move on; sometimes raise flop, sometimes raise turn, but in this hand fold on the turn without a h. Donks generally aren't 'middle pr' as much as they're 'weakness'. But here he barrels big and you have 0 backup. Calling turn is a leak.

Tariq Haji had a recent Video where he discussed this topic and made an analysis of the 100NL ignition pool and his donk-tendencies. He provided a chart at the end of this video with the conclusion that these bigger sized donks are mostly top pair or air.
with this in mind i guess calling flop and turn is fine, but almost everything of his air on the flop got there otr,