Oh my, you do have lot going on! Your health, physical and mental, should be the highest priority, in my opinion. I'm glad you have a diagnosis and plan for treatment.
I would suggest that you migrate your payroll clients to another provider/service midyear rather than waiting until year end. It will be less stressful for you and you can be available to help the process. My guess is that your clients will appreciate the care you are providing as you have for all the past years. I would also guess that the potential loss in revenue would be not so much while easing the stress you would otherwise be having. You could assess a charge for assisting in the migration and helping clients choose the right provider. They will have to make changes anyway and may will be grateful for your hand holding on the path.
When I decided to stop doing business returns and payrolls after my other CPA assistant retired, this process worked well for me. I still retained several for individual return preparation and some chose payroll services. I believe they all appreciated a transition period, my guidance and oversight and lack of abrupt change.
Best outcome wishes for all of your future moves.