Put yourself first ♥️ Give yourself and your health the time you need to recover, you'll never get anything else done if you don't.
As for the other - if you're expanding the story that much there's no shame in making it a separate - paid - game. The cost of it needs to match the work that goes into making it, if you have a story idea bigger than a dlc don't be afraid to just run with it just because you worry about upsetting people. Some people will be cranky, no matter what you decide, but I find the idea of a sequel/follow up exciting. Do what works best for you - and your health!