PREFLOP: Getting potentially 13-1 odds to call, I would call with K3s, the pot is too big to consider folding this hand despite your bad relative position and the small chance someone may LRR.

FLOP: The pot is so big right now I dont think it matters much whether you bet this flop or check and call. But if you are checking this flop becuz you fear MP2's hand, then I dont like it. Given the preflop action you should realize that the MP2 does not have a strong hand, he limp reraised after two people initially called in front of him(this means if he had a monster hand like AA,KK,QQ he wouldve raised right away since he already has his market. When somebody limp reraises in this situation it almost always means a speculative holding that plays well multiway like 55, or T9s.

TURN: Your check on the flop actually set you up perfectly on the turn to protect your hand. You should definitely raise this turn, the SB couldve easily played QQ this way and thats the only excuse you need to make raising correct here in this large pot. You dont need to think of yourself as a favorite before you consider raising in this spot. The pot is large enough where you only need to have the best hand a small percentage of time to make raising correct. A raise is vital to protect your hand from the gutshot/5 outer draws the times your hand is good.

RIVER: If you dont improve, check it down.