I just did one test with my mouse and eventGhost, using the genericHID plugin and did not have much success. I will try again with another mouse.
I think you should be able to pick up a cheap usb game controller and use that (or even find one lying around somewhere....) I suspect that will be easier, more effective, and less likely to interfere with your other mouse. Also, might be easier to rewire it to use a custom button that is easier to press.
If you don't mind waiting for the slow shipping, you can get some really cheap on ebay, from china. Maybe grab two in case you break the first one when experimenting
Or for a little bit more you can probably get something pretty cheap on Amazon etc.
About your usb mic on the ceiling. How far is it from your mouth? Anyway to get it closer, and also turn down the sensitivity (input volume)?