I have been where you are. Our most recent novel began as fanfic, and we took the fanfic off of the web as soon as we submitted the original. Also, like your piece, this one has turned into something of a monster. New ideas set in the same world keep cropping up no matter what we do. We plan to keep writing them, but we're treating each subsequent story as a complete and utter stand alone, just in case any portion of it doesn't get published. It allows us the play with genre, too.
As for your rights, you sold First Electronic Rights and one year of archival. Feel free to resell the story as soon as you like, but you will have to sell it with the caveat that it has been published before. Always emphasize that it was printed on the internet, especially if selling to a print publication. Some editors are more accepting if the reprint comes from another medium.
As for self publisher... My ex-co-writer says she'll self-publish everything from now on. She also has hundreds of copies of her novel in her garage and a maxed out credit. I don't understand this root, but some people do well with it. Myself, I think it is better to have freebies on your website at a lower cost that may attract people to /buying/ others.