Against unknown, Id rather bet/fold $7.50 since - until he calls on turn - we should see ourselves as ahead and try to extract value. Betting 1/2p looks a bit weak and we look like we are ready to be taken off the pot.
Once he calls on turn ch/f river looks fine. He probably doesnt turn his made hands into a bluff often enough for us to bluff catch, so we are mostly facing a flush/2pair/set when he bets the river.