Your symptoms are somewhat similar to what happened when my IAC was sticking: Low idle speed, only a problem when hot, truck stalls when trying to move in gear (because the IAC can't compensate for the extra load on the engine when you shift the transmission into D or R).
From your last response, you said hubby replaced the IAC. Q: Did that have any effect on the problem, or is it too early to tell?
If it didn't fix the problem, the next time the problem happens try this:
In Park, verify that the idle speed is too low (the speed should be about 730 rpm in Park). If the idle speed is too low, carefully and slowly push the throttle pedal down to see if you can get the idle speed back up to about 700-800 rpm steady. You should just need to barely move it. If this brings the idle speed to normal, this suggests that your IAC is sticking closed and not letting enough air in for proper idling. If you have to use a lot of throttle to raise the engine speed, then something else is the problem.
BTW, my opinion is that it isn't that likely to be a fuel pump issue because the flow needed for idle isn't very high. A fuel pump issue would be more likely if you were having problems accelerating or pulling a load.