You might find much cheaper winter storage rates if you are willing to sail the boat a short distance away from Annapolis, which has some of the higher boating-related costs in the area.
There are some reasonably priced haulout and storage fees advertised on Craigslist and in Spinsheet.
Indeed. Rockhold Creek Marina is nearby, in Herring Bay and has very reasonable rates. They allow DIY maintenance, and have electrical outlets scattered through the yard, so that you can power your tools and worklights.
You might call them and ask if they have room left for you, and if it's too late to haul you out.