Advice on my Wisconsin Miata

Hey all, I was wondering how big of a concern the rust on my NB is. I bought it at a great deal and had a fun summer with it, and now I'm debating whether I should keep it so I can work on it in the future, or sell it for a daily suited for Wisconsin weather. I don't really know how bad the rust is, so I have the pictures attached in the problematic parts. I also think there may be a leak somewhere, as I've noticed a musty smell sometimes around rain, and water is sometimes under the driver door when I open it. The worst spot is pic #3 on the driver's side where there's a clear hole, so I'm worried about the frame keeping up. I'm not as knowledgeable on cars or Miatas as I'd like to be so Id appreciate the help! If the rust is something that's not too big a challenge to fix I would like to keep it because I want to do a turbo setup when I have funds, but I need another car for that anyways when it inevitably screws up. P.S I am storing the Miata this winter because I don't want to die in a Wisconsin snowstorm and make the rust even worse.