Well this is certainly an interesting thread, and it has generated a lot of kerfuffle
Anyway I think what you are doing is great but I honestly do not see you being able to pull this off in Amos. The only way you'll manage this is if everything is done in pure asm.
I have viewed your demo, and yes it wraps around, but there's no sprites, no music/sfx, no enemies, collision detection and all that other jazz!
Getting this to run at full speed at 50fps with everything included is IMO near impossible.
You need to forget the music for now and actually get a playable sonic game without it, you will need to consider mod size and that for memory/speed purposes but to include it at this early stage is not important.
There's so much you need to do/consider before the music!
I would love for you to prove me wrong though as I always wanted to see that Amiga could do sonic (a500).. AGA machines I am sure could handle it, but again 100% pure asm is the only way!
Good luck my friend and welcome to eab!