David, first thing to do is contact the power company about the damage they caused to your tree.
You have a few choices in how to save this tree.
1) Do nothing till winter comes and see how it recovers on its own. Then you can prune where you need to or just leave it to grow as is.
2) Use some Elmer's glue to cover the bare wood so bugs don't get in. Tar based sealants are the worst thing ever invented, Elmer's will allow the tree trunk to breathe and it doesn't stop the tree from being able to callous over the wound.
3) Prune the tree back to a solid, healthy branch which will then become the leader. If you do this one, you will need to remove the basal suckers so the tree can put all its energy into the top.
4) I would prune off the basal suckers, the only reason to keep them is that you want a bush instead of a tree.
There are two trains of thought when you do major surgery to a tree. 1) leave the exposed wood as is. This thought allows the tree to weep sap to cover the exposed wood all by its self healing comes along well with this method.
2) paint the exposed wood (only the exposed wood, not any of the bark) with Elmer's glue. This forms a breathable seal over the exposed wood to keep out boring bugs.
by not coating the bark, the tree can form the callous it naturally wants to do and the tree will heal nicely. The Elmer's is not weather permanent the way the black, petroleum based coatings are.
Elmer's is what bonsai growers use, it is safe for the tree, it doesn't slow down the natural healing process, it does keep insect pests from gaining a foot hold or worse in the tree's wood.
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