Have you tried these forms of magnesium? This guy claims:
"The most absorbable forms are magnesium citrate, glycinate taurate, or aspartate, although magnesium bound to Kreb cycle chelates (malate, succinate, fumarate) are also good"
Consider making yourself bone broths, for their easily absorbed minerals (including magnesium) and other nutrients. They taste extremely good when made at home.
I bake a chicken, then boil the carcass in water with a tiny bit of vinegar, for a day or more, to get a gelatinous broth. It comes out better when you cook the bones first, then boil them. The vinegar helps leach the minerals out of the bone into the water.
I don't believe any condition is "permanent." You may lose function in your legs, for example, but there's always something that can be done to improve life. In that case, nerves may regenerate. Believing that conditions can be changed leads to a more positive outlook on life.
The important thing is to get as clean & as nutrient-dense a diet as you can afford. Beware of some veggies (celery & lettuce from California, for example) grown in phosphate fertilizer rich soil. That will get in the way of absorbing magnesium (the phosphates) and will make matters worse in other ways.