This is great, congrats! How did you get your first few customers? How do you plan on monetizing? I realize Peergrade is free, but, as an educator, do you have any advice with respect to selling into K-12 vs higher-ed?
I was in a very similar situation 6 months ago. If you have a typical agreement in place (4 yr vesting schedule w/ an initial 1 yr cliff), about 10% is not only reasonable, it's what you're legally entitled to. If you're legally entitled to 10% and you believe the company is going to increase in value and eventually exit without you, it would be foolish to sell then your stake.
Something like this: https://github.com/IBM/MicroscoPy
What you're describing sounds like it could be more than burnout though. I would also try to find someone to talk to.