I am really not good at facing donk bets, especially from villains that never open raise. I actually just posted about a similar spot on this forum, and one of the better responses I got was that a pro did a study a found that donk betting is weighted a lot towards top pair and air. Personally, I have seen a lot of donk bets made with already made hands. Villain has a good amount of 2 pair (KT, KJ, JT) that beat you, some sets (KK, JJ) , but the tough part his a lot of his air/worse hands would have a Q in it (AQ, QQ, KQ, JQ, even QT) which are now straights and beat you. The only combo I can see you him barreling for too thin value would be AK and AA, and now its pretty easy to see youre losing a lot more than you are winning. In fact im probably folding the turn since your K is pretty weak and even if you peel a 9 for two pair like you did it makes all the straights I just mentioned.