Had several furloughed United Airline Pilots at my interview. Infact, all but 3 or 4 of us were furloughed Airline, and there were 19 at the interview. I believe they all got hired, and I did not. So I would say that you have a pretty good shot at getting a position with one of the Fracs, especially the largest one. They seem to love the Retired and Furloughed Airline guys and gals. So if you need to stay current until United calls you back, send your stuff to NJA, they'll hire you. They don't care about the training cost! What company would hire retired airline pilots if they were looking for people to hang around?
To answer your question about the seniority number, I think you can get help from your United buddies on the resignation thing. The guys I interviewed with didn't seem to be worried, they were all going back when called.