There's a page here about using MIDI through UAE:
http://fromwithin.com/liquidmidi/uae.htmlIt talks about Bars & Pipes, but it should be applicable to OctaMED too. (Incidentally, you might like to find a copy of OctaMED Soundstudio - it takes a couple of weeks to get used to, but it's worth it.)
You shouldn't encounter any difficulty reading DOS disks on your Amiga. Format a DD disk (any old Amiga disk will do) on your PC, choosing 720K format.
On your Amiga's HD, make sure the "PC0" icon shows in your devs/dosrivers drawer, and you should be able to read/write using the disk, using the pc0: handle wherever you would normally use df0: