Last night I started taking the tapestry off of the loom. Thought I should stop at one point and refresh my memory of how this would best be done. I have decided to weave the loose ends that are sticking out of the back into the weft before going any farther with the cutting down the tapestry. If that works out to be too difficult (given the tension on the piece) I will continue cutting it loose and tying it off and then tuck in the loose ends once it is off the loom. I think the best tool for that would be the threaders for punch embroidery needles that I have. They look like giant sewing needle threading aids. I can easily slip them between the weft yarns, catch the loose ends, and pull them up between the weft yarns in order to bind them in and hide them.
I did run across some encouraging information - since this tapestry is woven with wool it may be possible to somewhat correct the draw-in/selvedge issue by steaming and blocking the piece.
It is worth a try.