Welcome again, Laura. You're right, this is a wonderful place. Never give up trying to find the reason for the RSD. Finding a doctor who will help you with this is even harder than finding someone who will help try to relieve the pain. Inquiring about finding a cause I was told more than once, "We don't do that." Huh!?
If you can find the underlying reason the nerves are inflamed you might be able to treat it and the nerves can return to normal. Just keep doing the research and looking for those who will help. Don't bother with those who won't.
You're a very special person to be so involved in your husband's pain. I think many spouses get overwhelmed with the new responsibilities as well as the loss.

KYIMP