Couple of points about the hand

1. You say MP1 is a friend of yours - what range of hands will he raise 6BB preflop with ? If he is a tight player that only makes this raises with PP JJ+ and AK you should fold preflop.

2. Villian raised big preflop and raised big on the flop, the 0.6 raise on the flop is 1.5 pot size, it looks like an attempt to buy the pot - the hand range I would give him credit here are PP TT+ and AK/AQh.
So when the A of heart hits the board I dont think you should be worried too much about a flush, the only hand you should be worried about is AA, and I would be willing to pay the AA here. However what you should be worried about now is an overpair with an heart, and the last thing you want to do is give villian a chance to complete the flush on the river - I would push the turn

3. On a sidenote, villians call on your flop reraise was a bad play on his part with the overpair, he should have raised or folded, but calling does not make much sense here