If you're not quite sure of the intention of the note from your business partner, would you feel comfortable discussing it?
That aside, how do YOU feel about your working environment?
If you left that partnership, and started out alone, might your clients go with you?
With regard to the work - life balance, I believe, where possible, do more of what you enjoy, less of what you don't.
If you have to do something you don't enjoy, can you do it differently, make it more bearable?
So, maybe, your new business venture?
Hope you work something out.