Ahahah oh man, the pain! :(
Yeah, text-editing .s files was annoying as HELL.
So you've got the hang of it then? Haha...
Well, yeah if you cancel out the midi events, it should just play one instrument, so that way you don't have to insert other midi events to "trick" the ROM into thinking it's an instrument...if you know what I mean.
Ahahah... Yes, there's an option in Anvil in the tempo, where you can go to a spot in the song and change the tempo there, or have a consistent tempo through out the whole song. :)
No worries!