[BillD]

Hand1: should have raised from the SB and bet out. Now just call and check call the river, unless your pretty darn sure someone was slowplaying a set. Your getting 8.5:2 on your calls assuming everyone calls. Top pair probably would bet the flop. MP could be raising on a smaller pair, or be putting you on a bluff. A3s, K3s could be possible, but wouldn't he have steal-raised preflop?

Hand2: call the flop, top pairs aren't folding and your not going to fold your overpair. check/call the turn and river. Don't set yourself up to bluffed off the pot.