How bad was this?

[Rduke55]

Home rebuy tournament. Down to the final 6. 4 pay.
Blinds are 2-4K. I am just above average at about 80K but 5 of us are essentially even. One short stack has 25-30K. Folded to me on the button. I have K7 off. I've been stealing pretty liberally and limp. I know, I know. FOLD PREFLOP! Someone will still say that. I KNOW! It was 1am.
Anyway, limp, the SB (1K less than me - can you guess how I know that?) and BB both call/check.
Flop is 4c5d6c. I bet out 6K. SB calls, BB folds.
Turn is a 3h. I bet 12K, he raises to 30K. He can be fairly tricky. I was thinking the only hand that beat me was 78 (and I have a 7). I actually thought it probably was a split and/or he was semibluffing a flush draw. Since I bet 1/2 pot on the flop I thought he wouldn't think I was going for the str8.
Since I figured all the money was going in the center if the river blanked or I couldn't call if a club came I pushed. He called and rolled over 7c8c.
Reason I'm posting is he said I should have laid down to his raise. I'm not sure. After the bad preflop call I can't see how I don't go broke here unless he raises me on the flop.
I just feel like hands like this are keeping me from improving to the next level.