One thing that would help future updates, if/when you give up on the project, is when you post it someplace (you are going to post it someplace like aminet, right?) then make sure you document the changes made to your stock version of the SDL code. This way people can do a diff of what needs to be changed when porting to newer updated versions of SDL.
Encapsulate these changes and document them while they're fresh in your mind. Oh, and great work!