Do you think acquainting him with the dialysis unit (I hear they are very depressing - helpful in this instance) might help? I have heard dialysis nurses often request transfers because working there is such a downer.

And not only visiting but talking to dialysis patients? If there is a chance that eliminating (at least, much reducing) salt could make a significant difference in whether he could avoid dialysis, they might be quite persuasive. Having to be hooked up to a dialysis machine for hours several times a week, is just awful.
Maybe he doesn't have a real-life picture of what he's doin to himself.

My father died of kidney failure, and as a foodie he really suffered from all the food restrictions (including, of course, eliminating salt). I decided to reduce my salt intake* some years ago, and although it was hard at first, I really got used to it. (Same with sugar too, but that's another story)

Experimenting with a gourmet nutritionist cookbook (perhaps the burden would fall on you) might help him wean himself from salt.

*I'm greatly helped by using potassium "salt" instead (doesn't make a noticeable difference to me). It seems to have also majorly helped my cardiac health (also magnesium supplements). Hadn't realized how important it is to keep up ones electrolytes.