Ugh, I feel you, mate. Try Scribbr or Editage for legit editing help on your dissertation. They're solid choices for polishing up your work without any shady stuff. Hang in there, Burnout Senior - you got this!
I used Scribbr for my Master's personal statement last year and honestly it was worth every penny. They let you choose an editor with expertise in your field—I picked one who specialized in social sciences and she gave me feedback on both grammar AND argument flow.
One tip though: leave at least a few days for revisions. I sent mine in thinking one round would be enough, but the editor's suggestions were so good I wanted to rewrite half the essay Took another 2 days to implement everything.
Also—if budget is tight, see if your uni has a writing center that reviews grad applications!
Took another 2 days to implement everything.