The calcium binds to phosphorus which is deadly to those in renal failure. As you already know, nothing can cure this disease, so all you can do is manage the symptoms
as best you can.
If you can stand it, check out the several journal articles I wrote on my profile here at Med Help regarding Chica and our "adventure" with end-stage renal failure. You and your husband are doing the same things we did, and your Sandy Grace sounds like the exact same temperament as our Chica.