Yes, I did get it out. I hooked a cable to the backhoe frame (near the centerpoint) and used a 2000lb ATV winch tied to a tree to stabilize the tractor rear end. The winch didn't have the power to to anything other than "hold things in place". I did move the BH boom all the way to the uphill side to shift the weight after I got off and saw the "whole picture".
The BH stabilizer on the downside was useless because it just sank in the dirt. Using the BH to raise the center of gravity made the pucker factor surpass even my newly recalculated limits, so I quickly gave up on that one.
However, after the back end was not going downhill anymore, I was able to get the front end pointed down so the angle of the tractor was more "up and down" instead of "side to side". Then, I could use the BH boom to raise the back and put the tractor at at complete 90 to the bank.
With the tractor parallel, the winch, curling the bucket, and using the diff lock enabled me to get the rear tires back on solid dirt where I could pull out of the situation. Took about 2 hours, inch by inch.
The trees aren't completely vertical (the picture is about straight), but yes, it was feeling quite tippy and my mind was reviewing all the events of doing a slow roll and how the ROPs was "supposed" to protect me. I must say, that it was a tuff decision to keep the belt on vs. preparing to jump off on the high side. I think discussions on this board made me do what didn't feel natural... keep the belt tight, implements low, and move ever-so-slowly. Hey... it worked.
Ironically, I have a tilt-meter and it came loose from the mount the day before this happened. I don't think I would have had time to look at it anyway in this case, but I'm remounting it today. At least I could have seen how high it would go on a B7800 if it had been mounted.