desideratum

I'm employee #4 at a pre-seed startup. Their main offering is a digital continous improvement solution targeting large corps. Employees #1-3 are all app developers. Significant projected revenue for the company revolves around the mass collection, processing, and analytics of data from their application.

I joined after dropping out from my PhD as the only ML-data engineer and to own the development of that product space. I've completed a large (~0.7M) govt. grant in the first few months of working here to support development of my product with collaboration from academics from my alma-mater, and began hiring engineers for this project.

I'm currently earning ~£22k (UK, non-London) and they've just offered me 0.1% in options (EMI scheme). They (founders) specifically advised against sharing details of options with other employees but I've discovered they've lowballed the lead frontend engineer also (<0.5%). They further advised that I can ask for excess of 1% in 12 months if I can take on tech lead responsibilities, but this isn't in writing and the process for this is completely opaque to me.

Is it worth sticking around here? How can I negotiate a (much) higher total compensation for myself?