i call it off because i expect him to check back KK on the flop if he checks back AK and vice versa (equal # of combos). however it would be a bigger mistake to check AK than KK, so if we discount KK by one combination then we'll have 2:3 or 40% equity and it's probably close to a fold. cbf on the maths because my brains fried

edit: this is in response to H1, hadn't read any more of the thread at time of posting.