You're really not thinking this through.
OK, yes, you can assign MIDI control to channels via note ON, but it's not really all that graceful. MyDMX will take the note on and the velocity data to generate a DMX value to the channel, but then you have to issue another MIDI command to that DMX channel(note value) wiht a ZERO velocity value. MyDMX will NOT acknowledge note OFF commands. This has been documented.
Are you looking for FULL automation? MyDMX isn't intended for that at all.
My suggestion:
Use not values and/or patch change for scene calls, and then use CC's for stuff you want more constant control over.
Use scenes. You'll get better results for triggers, which is what you want.
DO NOT assign notes to channels, as you can see what happens.
But on the DMX channel/MIDI Note issue:
A recap: yes, it will use the velocity tied to the note ON to generate a DMX value at a 2:1 ratio. Each MIDI step(1-128) will equat to a DMX value of 2X(velocity).
But, that also means if you pound the snot outta that note, you SHOULD get a FULL on. And if you can do a halfwaay value(velocity = 65), you will get a DMX value of roughly HALF, but that doens't necessarily equate to a half-intensity setting in DMX, as that's fixture dependent. Don't expect a 50% DMX value to necessarily equate to 50% output.
If you get out of this need for total control, you'll be fine.