When I was diagnosed, I had high calcium levels. But I also had a lot of other problems including my kidneys shutting down. One of the big concerns with high calcium levels is that it can have effects on your heart. It can also effect your mental status.
I did feel really crappy during that time, many of the same symptoms you mention, but I'm not sure what caused what. They got my calcium levels down by flushing my system with lots of fluids. I did feel much better when they got these under control.
Good luck with getting the right treatment to help him through this time.
Janet in Idaho