The USB microscope would probably work, as long as you get it angled right. I use a document camera at work as an alternative to writing on the whiteboard, and it works really well. It's basically just a little camera on a stand with a video out (HDMI or VGA) that we hook to a projector, monitor, etc. There is no delay, and it's pretty easy to learn to manipulate objects under the camera while watching the screen. I don't know how much it would cost, but they have come down in price substantially over the last few years. My only advice would be to find one with a video out instead of USB, so that you can attach it directly to a monitor.
Good luck - it can be hard to find solutions to mobility limitations, but it sounds like you're on the right track.