I would say that a 30 degree bag would be grossly inadequate for what you are proposing-- I have occasionally found my 30 degree bag barely adequate in April and October. The 20 mile days also sound overly optimistic-- with the very short winter days, and the hiking in sand and route-finding, I would think 20 mile days would be hard to accomplish, and leave very little time for appreciation of your surroundings.
Okay, that comes out sounding pretty negative.... Have you considered something a little further south, maybe Arizona? Less risk of having to deal with snow, and your bag MIGHT get you by down there..... Or somewhere in southern Calif.?
Good luck with your plans!