1) No, it's important to have the feet flat on the floor during meditation, so you remain in contact with the telluric currents. That's why the chair is recommended.

2) A brief interruption isn't a problem -- just go on with the working. With anything that distracts you thoroughly from the work, though, it's best to start over from the beginning.

3) Fascinating. No, I haven't encountered that before and am not sure what to make of it.

4) I know people who get excellent results from it, but it's not something I can do at all well. Maybe someone else can suggest something.