Burning Skin and Spinal Nerve Root Disease

First question: Without seeing you face to face, I cannot answer your first question with certainty. Diffuse burning of the skin is not a typical symptom I would associate with rheumatoid arthritis. If the sensation of burning is not associated with any rashes, it would also be less likely to be due to discoid lupus. Some people will have these symptoms if they have underlying blood disorders (polycythemia vera, e.g.) or nervous system disorders (dysautonomia, e.g.). If there is flushing associated with the burning, certain medications (Niacin) or hormone-associated tumors (carcinoid syndrome) can cause these symptoms. Basically, I don't believe this to be a rheumatology problem. If you have not had a basic evaluation through your primary care doctor, I would start there.

Regarding the 2nd question, nerve compression in the spine due to bone spurs, disc disease, or scar tissue can spread or worsen but does not always do so. Worsening of the nerve pinching could occur at the same level or at different levels if there is degeneration elsewhere. If you develop any new symptoms that radiate down your legs (for the lower back) or arms (for the neck), you should have this problem re-evaluated. To prevent further deterioration of the spine, low-impact exercise to strengthen the core muscles and weight loss if indicated would be good strategies.