A stable 5k/month cashflow is worth maybe 1.5 million dollars flat. Ignoring the phenomenally unethical effort to part ways with you one month before the cliff, you rightfully own about 9.16% of that-- or on the order of 137k. You could argue that up and down based on risk and operating cost vs the potential to increase it, but I think that would be a fair starting place for the present realized value that I'd hope to negotiate from.
Have you talked with your investor? They may be more sensitive to the consequences of their reputation being damaged due to ripping you off than your cofounder is...
Have you talked with your investor? They may be more sensitive to the consequences of their reputation being damaged due to ripping you off than your cofounder is...