Bushy Birch

I have 2 birch, and this one is the one im the most uncertain of how to proceed on.
Its totally potbound, so I could just lift it out and put some more soil/litter around it, so the water doesnt run straight out at the pot sides.
I can see that at the trunk base, there is some clay. I dont know how much but is it safest to let it be over the winter?
I plan on putting the tree in a more shallow and wider pot next spring.
I cut the tree back and had very nice growth, so I cut it back some more. The major problem I have, is that there is a terrible case of
inversed taper up the trunk, after the trunk splits. Should I cut it back and make a much smaller tree? Maybe at the other trunk? Or make it a smaller tree at maybe 10-12 inches? You can also see the tree has risen in the pot, cause of lack of repotting..
Maybe only a "v" cut beneath both main branches would be the way to go..
Oppinions are much appriciated. (The root at the tip of the scissors are planned to be cut.)








Sincerely, Storm.