Hi Gina!
I was in a similar situation and your doctor sounds like he knows what he is doing.
Stage doesn't really mean anything in the long run. Many stage 1 and 2 have not survived. Many stage 3 and 4 have.
The odds are really 0% or 100%

I wanted to avoid radiation at all costs before the surgery, but when 1 node came back positive, (even though it was removed and encapsulated) the thought of a cancer cell roaming about was too scary, and I have a big fear of anything medical. I didn't want a recurrence. I only had to have rads.
PET scans are notorious for false positives too soon after surgery, so I wouldn't worry about that too much until the surgery is over and the results of your nodes are determined.
But I would for sure go for the rads if any are positive. Chemo is something I didn't have endure.
Oral cancer can be beat. Give it your best shot. Do everything you can to rid yourself of this disease.