Was very unsure how to play this particular hand postflop, am curious what you guys think.

Prefllop 100bb deep I think 3b vs. the btn open is quite standard. What I'm not sure about is the correct sizing. I see a lot of people in the pool going 5x OOP v LP opens. I decided on 4x, is this universally considered too small?

On the flop I think this spot is quite tricky. If I decide to bet (which I'm not sure is the best option), should it automatically be presumed that it's to get in stacks on flop if raised?

Check calling is of course an option as well, and perhaps without a diamond it's the more prudent play.

Finally, sizing on the flop I went 2/3 largely because of the draw heavy nature of the board. Any arguments for different sizing?

Also, is there a way to fold this flop once I've bet//been raised?

Thanks,
gaucho2121