Only time will tell if you get regrowth from what's left. Some varieties regenerate pretty easily, others do not. A good amount of sun does help regrowth. Do you see green cambium just beneath the bark? If yes, there's hope. If not... Do not attempt to seal the cut ends with glue or anything else. Cut branches at an angle to shed water, though. I would cut back closer to the ground, but not to ground level. The large branch on the left is particularly awkward. If you get new leaves, do not allow the plant to dry out over the summer. Be patient. Probably 5 years until it looks decent.

MG- thanks for the response. No green cambium.

"Cut branches at an angle to shed water" - this is good, general, advice. Something I'd never considered.

"The large branch on the left is particularly awkward" - agreed. It's modern art. Really though I have some folks coming to do some tree work so I was trying to make it patently obvious to leave this alone.

"Probably 5 years until it looks decent" Well, I have time (Lord willing). It's not in a good spot for me anyway, so no big loss. I'll leave it be with some mulch and see if there's some miracle. I'll update if anything happens.

Thanks again for responding.