Does H8000FW respond to Midi CC learn?
Yes, but on the H8000 it is called MIDI Capture. See the UM for more info.
Is parameter changing limited to controlling one per channel / per track?
No, you can have as many as you want (within reason).
I am not using a keyboard – does that mean i am limited to sending and recieving "note on" midi messages?
On the contrary – the H8000 does not do much with "Note On" messages, except for a few keyboard related presets.
It mainly uses MIDI CC (Continuous Controller) – look at the manual for your MIDI setup to see how to send these, then the H8000 UM to set up MIDI Campture to make it easy to recieve them.