If you miss coding for month or two you will need to start over. It's not like learning skiing. You have to sharpen your coding skills on a daily basis.
You are too kind and very naive. By what you wrote, those people are taking advantage of you and abusing your knowledge and time. You supposed to say something while ago. They saw that you are not making any comments and you are not raising your voice. And then they thought, OK let's use this guy as much as we can. If they weren't thinking like that, they would offer you a fair compensation long time ago. If there was not enough cash, then at least in some shares. Their plan was to use you to the point where you are not needed anymore. And I think that is when they employed new full time CTO. I think it is too late to do anything now. If you don't have anything on paper you will gain nothing for you previous work.
Thank you very much for your reply! It is very informative and useful. Somewhere in back of my head I presumed all of this. But I didn't know that comments can be also down-voted. Anyways thank you for all of these details!
Very nice design and UX. I like it. What would be nice to have is a switch (like remote switch) for part-time jobs. Keep up the good work! And thank you for this service!