Pre flop: I think this is fine. You want to get others out behind you, even though it doesn't work you have to call the capped pot.

Flop: Like what you said, I would normally raise this. You aren't worried about MP3 as he checked his posted big blind the first time around.

If you get 3-bet in this position, would it be ok to call-call-call through the river, assuming no ace falls?

Turn and River: I play it the same way. From his stats and history, he is just as easy doing this with A-x as he is with KK or QQ.