Sorry to hear Grad School has been set back for you too, but good to know you’re taking care of yourself.
The online aspect of my coursework was nearly like a course in itself 
, so take advantage of any advanced access you might have to learn to navigate that before your actual classes start.
I know you follow @ChristopherFritz’s study log, so to get back in the swing you could do as he did and have just 1 lesson a day to have forward movement without too much stress.
I was determined to not do lessons until I got caught up on reviews, but then saw another staff post about new additions and realised that the new low-level stuff should be far less taxing, so I’m doing 3 lessons a day. Because of my review backlog, I installed 2 new scripts; [Userscript] Reorder Buttons, and [Userscript] Wanikani Wrap-up Button Enhancement, which together allow me to do my apprentice items on time while chipping away at my more advanced items over the next week or so.