I was only on methadone for a short time, but I've been on other strong pain meds off and on for nearly five years, and I've never experienced the kind of pain that you are describing when I went off any particular narcotic.
Why is it that your doc can't prescribe a break-through pain killer for you to take for your facial and back pain while you wean off of the methadone? When I was taking methadone, I was also given dilaudid for B/T pain. It might be helpful to ask your doctor about that.
I didn't get very good pain relief from methadone, which is why I went off it. I hope you manage to get this sorted out and find something which will give your better relief.