Holy cats! Mrtree started off unchained! Not the personality of the board I remember at all.
That tree looks cooked, but I can appreciate a pet project. Removing girdling roots is a bit of an afterthought in this case - it would be more appropriate about 15 years ago, or more obviously, the proper planting depth would be the best.
At this stage, avoiding water stress would be key (both droughts and floods). You're more or less on hospice care at this stage. I say that because I've removed girdling roots on nearly dead trees as an experiment myself, but I feel it just removed the only living roots left on the tree.