Once the dialysis begins, (basically a substitute for his kidneys) his blood pressure will get better (less fluid to push around because the dialysis will get rid of it), the water weight will start to come off, his heart function will improve (again, less fluid to push around in the blood stream) and he'll generally feel better. Insulin will maintain his diabetes, but diabetes is a tough disease for the kidneys and the nervous system--the neuropathies in the feet, etc.
Dialysis causes some electrolyte imbalances, so I'm sure they'll be watching that....he'll most likely be given a LOT of supplements to take....
Hang in there!