Renee,
I think it's important to remember, when you are beating yourself up about this, that you didn't ask for RSD, you didn't want RSD (heck, most of us probably didn't even know what it was !), and you didn't do anything to "deserve" developing this.
We still have to apologize if we've been extra irritable/snippy

and during periods of some control over pain levels, it's nice to try to give your partner some extra attention and thank them for what they do.
My marriage was in trouble long before RSD raised it's ugly head, so I don't think I'm qualified to comment more on what to do to make a marriage work, but I very qualified to say I KNOW that feelings of guilt and being a burden make our pain issues so much worse.