An adjustable bed base is fine for sitting up to watch TV, but for sleeping, the bed needs to be flat in order to maintain your spine's natural alignment.
The Jacaranda latex mattress from Sealy, was quite firm and should be ok for your back...but it's too firm for your other issues.
If the mattress has worn, you can flip it over. The underside should provide all the firmness you back requires.
Add to that, a 2" or 3" soft Talalay Latex topper from either EverEden or Pure Bliss...shown here:
The soft latex will relieve the pain of your Fibro, Osteo and Rheumatoid arthritis.
Continue with your chiropractor. They do excellent work.
You might ask him about a product called "Bio-Freeze". It's topically applied, providing excellent and almost immediate pain relief.
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