Marginal hands, how do you play them?

[DonLigretto]

Hi

I usually play regular SNGs and not turbos and I always have problems playing KQ, QJ, AJ, AT, KJ, KT and QT. Usually I fold all of them to any raise except KQ in LP if I still have 20-30 BB and the raise is just 2-3BB. Otherwise I try to limp with all of these hands except if I'm in LP, It gets folded to me. Is this too loose or how do you play these hands?
In the last game I limped with KQ from MP with about 25 BB left, one guy before me and one after me limped as well, both had about 30 BB. Flop was K79 rainbow. the guy before me made a min bet, I raised 3x. He min reraised. There I should def. have folded I know, I pushed however and he showed K7 offsuit...

Besided the obvious mistake of pushing that hand, do I play these marginal hands generally wrong? At the moment I just have a really downswing on fulltilt (not on pokerstars though...) and that's why I'm just starting to lose confidence in my game...