I forgot to add one thing. If your opponent does not bet his UI AK-AJ on the river, then you can get to showdown much cheaper, since those hands make up such a significant part of his range. If we estimate that in those situations he will only bet the river 50% of the time or so the call down becomes +EV, even without adding combos of KJo:

EV of Calling Down =
A. (36/107)[(43/46)(-1.5BB) + (3/46)(6BB)]
B. (9/107)[(-2BB)]
C. (12/107)[(40/46)(-2BB) + (6/46)(6BB)]
D. (24/107)[(43/46)(-2BB) + (3/46)(6BB)]
E. (6/107)[2BB]
F. (2/107)[(14/46)(-2BB)+(32/46)(6BB)]
G. (18/107)[(6/46)(-2BB)+(40/46)(6BB)]

= +0.065BB

Finally, taking hands like ATo to showdown will discourage him to take shots at you in the future. So, I've convinced myself that calling down in this situation is best. One thing to note of course, this might change the expected payoff from the KJ/KQ hands, though he may likely fire one more bullet to try and get you to lay down ace hi.