After two limps, preflop seems standard. Pot seem about right for the isolation, I can see going a bit bigger also. I don't really feel like the size is a mistake but I am open to critique.

Preflop is just weird to me and shouldn't be something that happens to often but it is what it is.

What are your thoughts on best course of action facing a check and a donk bet of this size.

The unfortunate thing is that I have never devoted any time to spots like this since it should be a fairly rare occurrence so I am kind of in the dark with my reads/assumptions.