Magnesium and B6 work in the metabolism of good fats.
If you do not have a source of linolenic acid-- omega-3, the lining cannot heal itself. The omega 3 fats keep all mucus membranes flexible and an effective barrier to the environment.
Asthma and breathing issues also may resolve for you with EFAs.
I had both GERD and adult onset asthma before I started a good program of flaxoil and evening primrose with fish oil added. After 6 wks of all 3 my issues were gone and needed no more medication. That was over a decade ago, and now I reap those benefits every day. Today there are foods with these good fats added...but when starting out highly deficient, you need more than you can get in food. Say perhaps 3 flax oil a day (one with each meal), 1 evening primrose and 3 fish oil or 1 of the new Krill oil (you need less of this because it is better absorbed).

Some drugs cause erosion of the GI lining. Accutane is one.

Essential fatty acids are essential. Meaning we cannot live without them. I would use another form of magnesium, like magnesium glycinate. The citrate may be too laxative for you.

People with RSD really can benefit from antioxidants, like Vit C and grapeseed extract. These can lower inflammation.

It is hard to say after 24 years how much you can correct however. But I am ever hopeful you can improve to some extent at least.

You can PM me anytime.

Emu oil is high in Omega 6, and Omega 9. I have heard of people taking emu oil orally. You have to make sure that it has been refined from a FDA facility, but I have seen it in a gel cap form. This may give some relief to your internal issues.

From my understanding, if you have any inflammation, avoid high omega 6 and stick with higher omega 3 oils like fishoil and flaxseed oil as omega 6 promotes inflammation while omega 3 is anti-inflammatory

at least, that is what my son (who has Crohn's Disease) has been advised by his physicians