Stepping in a day late here, but I wouldn't be surprised if the cause was using straight water in the system. It's called coolant for a reason. All that vapor pressure caused by the low boil point of water could be what caused your radiator to fail. How far south do you live in Ca? If you normally run just under 210* with coolant, and you know water boils at 212*, and that even a simmer will make steam, what did you expect to happen? Even after seeing boiling water in the coolant reservoir?
The original pump is likley well worn. The impeller blades actually wear back with use. I don't know why they aren't considered a wear item.
But if you are doing engine work and it has 100,000 miles + on the pump, you (we all) should replace the pump and thermostat. Hoses too. If you think the front belt has a hard life, think about what those hoses have to go through. Replace the ones to the heater core as well.
I too am curious as to why there are no good aluminum radiators for the Jeep.
It seems the ones made for the Camaro Mustang and Pick-Ups all do well. What is different about a Jeep that causes apparent problems? Best of luck with the repairs. Out of curiosity could you check on how much wear is on the pump impeller compared to new? I've got 145k miles on what appears to be the original pump. Thanks.