I was dealt KK on Button. Raised 6x BB with 3 limpers and got two callers

Flop: 466 different suits

Limpers check to me and i raise half the pot. One of them pushes all in.

I put him on 44 but call because he's been pretty agressive. He turns over A6

Did i do anything wrong? How could i possibly put him on something like A6 and how can i get away from it?
--------------

Another question
Board was
4K787 with 3 clubs. I hate the ace-x of clubs and the nut flush draw on the turn. I called and the 7 of clubs came up on the river. I pushed all in and he calls and flips over 78

was i suppose to be able to muck that there and/or did i play the hand incorrectly by not folding? or should i just chalk one up for the cooler and realize i got unlucky?