I preface this with saying that I do not have that much experience with maples. But this is what I would do if it were my tree.
The deer damage doesn't look too bad. It is a bit hard to tell with leaves on the tree, but most of your branches look like they lack taper so cutting them back is actually the right thing to do. I would look at this as an opportunity to go through the entire tree. Reduce all the branches to only 2 at each node and cut everything back hard to improve taper. If you do it right it should look like a plucked chicken when you are done. I would seek guidance on when the best time to do this work in your area is.
The other thing I would do is start working on those roots. In the spring really work on getting things in shape. Remove any crossing roots and arrange the roots radially. Also work on reducing the depth of the roots. At this point the roots are much too mounded up above the edge of the pot.
I would consider creating a dam around the pot now and back filling with substrate to preserve the fine roots that are exposed. You don't want these to dry out and die back.
In no way do I think that this tree is a lost cause. With some work and some time this is going to be a really nice tree.
