Wow Jimboss, that's a few problems he has - but all totally fixable if you can get his mental state sorted out.
There are certain methods of dealing with addiction which hopefully you have under control. Blood pressure and diabetes can be fixed, we'll come back to those later but for the kidneys I'd flush them right out starting immediately.
8 to 16 oz good clean distilled or filtered water, add the juice of one lemon and one lime, a pinch of cayenne pepper and add some organic maple syrup. Do this morning, noon and night for 7 days, and have lots of water in between. Ideally eat only minimally during this time and keep it to raw fruit & vegetables.
That will flush the kidneys and dissolve & remove any stones as well.
If you can get them, dry the leaves of a peach tree for about 3 days in the shade, then chop or crunch them up & make a tea out of them, perhaps one cup per day while doing the above. This will strengthen the kidneys and get rid of excess fluids in the body.