How aggressive is too aggressive?

[Aviston]

Preflop: I'm folding 88 here. WIth your read on MP1 you are at best playing against two overcards. This is fine and dandy if you can get the hand HU. However, since UTG is already in, and as you say, is a calling station, the odds of a preflop 3bet folding him are slim.

Flop: As played, I'm checking with the intention of raising MP1's continuation bet. At this point I'd love to send two to UTG in the hopes I can have this hand HU on the turn.

River: Nasty card. You've stated that UTG is a calling station but folds to turn and river bets. I'd be willing to say that he'll be folding if he doesn't have a piece of the board, meaning that a bet here doesn't really seem to be for value. I'm checking here and calling only if you think he is capable of bluffing at the pot.