Well, I think that the next step to working with this is to give it a good pressure wash to get rid of as much mud, dirt and stones before I start to decide to cut it. Not having done a root ball is it best to hold it by the trunk end and make that the bottom. Which I would have thought is the best way for the stability of the piece.
If I remember correctly I believe it is an ornamental fruit tree of some kind cherry possibly last picture show leaves. This took the complete day to remove which would have taken a couple of hours when I was younger