Bet bigger pre-flop. I like the above sizing of $80. Biggest argument here is that its much easier to get money from people when they think they have a chance. Best flop you can hope for with AA to get called by legitimately strong hands are usually ones where you flop a set, and by blocking top pairs at that point, its much harder to get money. So get as much in as you can pre, which also gets other players out of the hand.
K94 is a dream scenario, and definitely a board you should be firing on, get hands like KQ KJ to call, and maybe some spade draws will re-raise, but with only one ace left and AKs not possible, they can’t be drawing to the nuts. As played, should definitely checkraise, charge his draws and top pairs.
Turn: this is where checkraising would have given us a ton more info on the flop. He is much more likely to have a K if he called our checkraise. But now we are guessing what he has. As played his $40 bet is fine to call. You get nothing out of leading.
River, almost certainly behind when he jams. The only reasonable hands we *were* ahead of he could have been playing this way seems like JJ or A/Q+10, and this J on the river means we lose to more of those combos. So this is a fold. UNLESS, you have been paying close enough attention to this player to see if he is capable of making bluff-jams on missed draws. While unlikely, He could try to steal with missed spades, or he could think he’s value jamming with AJ because he doesn’t believe you have a K. Reads will be important here to decide if there is a chance you are ahead. There are bad players out there, and some will make these kinds of moves. Tough to make the call, but they can be nice boosts to your chip stack.
-Sean