I’m sorry to hear that Mark and I hope all goes well for you.
I’m not qualified to give any advice.
This is a tough one because I don’t think that you can trust processed supplement type substitutes.
I’m not even sure about or organic substitutes.
I’m salt sensitive because of taste rather than health reasons so I can substitute or reduce salt with organic things like items from my herb garden and citrus from the stores.
I’m not sure if these would work for you so I would ask you doctor about his/her recommendations.
Citrus wise lemon and lime slices and juice are my faves but zesting other skins works good too.
Herb wise thyme, rosemary, basil and fennel seem to always find a way on my food.
There are also the countless peppers that I constantly use.
I recently became a fan of zesting frozen jalapeños on a bunch of things even hard boiled eggs
Salmon covered with lemon slices, veggies, with a light dusting of chipotle and no salt in a convertible aluminum foil boat on the bbq has never received any complaints here.
I’m even thinking about rigging a fish basket to my rotisserie and using simple herbs with mesquite heat for flavor.