jimgill, you may have given us a few clues. Your skin issues hands and thighs sound like psoriasis. The joints may be affected by psoriatic arthritis as they are often seen together. A dermatologist may be able to determine by looking at your skin during a flare, if not they should offer a biopsy.
ANA 1:80 is high but is common in people without autoimmune systems. The follow up to a positive ANA would be an ENA which could help to determine if and which autoimmune system is activated in you.
There a many medications topical and injectable which can relieve symptoms. If you have psoriatic arithritis you would want to protect your joints from the permanent damage they can cause.
I'm curious about how you will proceed.
Sarcopenia can be counteracted for some extent by careful attention to nutrition. Creatine supplements, D3 supplementation, sufficient protein intake for your weight and exercise can help.
I'd try to get the ENA from whomever ordered the ANA. If your internist isn't helpful, you might want to see a rheumatologist. I'd see a dermatologist as well. If the dermatologist can't tell by looking, ask for the biopsy.
Best wishes.