Seeking advice on offering equity to a key contractor

I'm developing my third SaaS. My first two SaaS have limited growth potential but provide enough revenue to support a small team of three remote contractors dedicated to this new project, which is my primary focus and hope for a breakthrough.

This product is technically challenging. After creating a prototype and validating the idea myself, I initially hired a developer who didn't meet expectations and was fired.
Seven months ago, I brought on a new contractor, and the difference has been stark. He’s very experienced. He works fast. He finalized the whole pipeline and solved many hurdles. He did better than I would have had myself, even if I had worked 100% on the dev. The way we work together is very fluid and efficient. I consider myself lucky to have him on board.

I believe in rewarding early employees and long-term contractors with equity, a promise I made during the hiring process. Due to a request for a raise beyond my budget, he's asked me to concretize the equity offer.
I'm considering a standard four-year vesting schedule with a one-year cliff. However, I am unsure about the percentage to offer at this stage, especially since we only have 10 paying customers at $30, making the company's current valuation zero.

Any advice would be greatly appreciated.