I've had a look at my preflop stats after reading your suggestions. My preflop 3bet % sits at 3.6, 4bet at 1.92%. Not sure how that 4bet translates to what Keith was suggesting in terms of villain seeing a 4bet as KK+ vs other ranges though?

I think he would have folded to a shove on the river, in the chat at the time he said to me "you have AK, I'm sure of it" a few times then "nh, I'm going to call anyway".

I'll rethink my preflop strategy here, and have another look at the turn. Thanks guys!