Just to be clear. This is NOT an addon issue. Healbot (or any addon) can only use the keybindings that WOW permit. I know it's confusing sometimes.
So you need to look at getting the mouse to work with WOW. You can look up the WOW or device forums for how to do this. If you can set the key bindings in the wow menu (Game Menu - Key Bindings) then it will work for any addon.