Id raise more preflop. In my experience at these stakes in live games 10bb raises are often called multiple times. if you raised less than 5bb with KK, then you certainly under raised them.

If I knew it would be heads up I couldn't fold to this shove since him having 79 for the straight draw or 99-KK are too likely and having put 1/11th of his stack in preflop he hasnt got too great an odds from you to flop a set and bust you.