Your flop raise was correct, however you called it "trying to steal", but that's not really what you're doing. You're raising because you either currently have the best hand, in which case you're raising for value, or because you want to force the third player to call two bets cold, in which case it's a protection raise. If UTG+1 has a gutshot draw or low pocket pair, you're making his pot odds too unprofitable to chase his weak draws. Monitoring his reaction to your raise also gives you information on what he may be holding. By the way, if he raises you there, it's hardly an automatic fold. I would call that one extra bet and see what the turn brought. If he is only on two pair you still have a chance to improve on the turn, or at least re-evaluate.

The turn card is scary, and even an idiot can raise with a decent hand. Against this guy, folding is probably not an option so it's call or raise. Raising here gets you in trouble if UTG+1 hit something or if the idiot actually has a hand this time. A 3-bet here would be bad for you. I would just call it and see what the third player does. If he raises, I could feel confident I'm beat (keep in mind that the K also set up an easy one-card re-draw to the flush so your hand value drops considerably).

On the river you mentioned your possible bad kicker, but you're not reading the board correctly. At this point, if he has, say, Q9, then you both have two pair (nines and sevens) with a K kicker. Because he was still timid when that K hit, and he has done nothing but passively call all hand, you absolutely fire a bet out here. Odds are you either have the best hand or at worse split the pot if he has a nine. Well that's my two cents! Good luck!