I don't know much about the brachial plexus avulsion.

I do know that our dog Cassie recently had a wound from surgery that we really had a tough time getting to heal because she just wouldn't leave it alone.  She had a lump removed and it looked good originally and then she licked it.  ugh  What should have healed in about a week or so took us almost 4 months of daily bandage changes to get to heal (and I don't know how much I spent on coban!  lol)  Our vet had us use surgical honey on it (manuka honey) - what he had was from Australia.  You can order it online from Amazon, someone mentioned they found some at a local discount store (TJ Maxx), but only once in awhile and I didn't find it there.  It runs about $20 for a tube.  When I ran out I found something at the store made by Curad that said it had silver in it - it's also an ointment.  So every day we cleaned it then put the honey or the silver ointment on then a piece of telfa gauze so that it wouldn't stick, then wrapped it in coban.  Coban is also in the dressing aisle in the drug store, with the tapes.  It's a self-adhesive tape.  You just wrap it around and it sticks to itself.  That way Cassie couldn't get the dressing off but it didn't stick to the wound either.  I really wanted to be able to let the wound air-out some, but to do that we had to put a cone on her.

I think checking with the rehab vet is probably a good idea - make sure that you are looking at all of your options first.  But if the leg doesn't have circulation, then it may just be a matter of time before there is more injury.   How old is Chester?  And how is he otherwise?  If you decided to go ahead with surgery, the first 2 weeks or so are the hardest, but after that they usually do much better.  Whatever you decide to do, we'll be here!

Donna