Why have you let it go for so long? This isn’t a new issue and it’s been going on for a long time. What does the CTO have? There has to be something because otherwise there’s no reason this should have festered for so long. Fundamentally, you’re a minority shareholder who has taken cash down to zero while waiting on someone who has never delivered anything. If the CTO has an immense amount of talent, that might be a reasonable reason to keep them employed. But if the CTO has different kinds of leverage over you and/or the patent, it could become a problem.
It would be worth spending a bit of time thinking that over. You’ll learn a lot for the next time you start a company. And in this case, you may be adding to your strategy to get rid of the CTO.
Have you spoken with a lawyer about your potential liability? If not, you should likely delete this thread, talk to an attorney and if you repost this, you should only include the information she tells you to include.
As well, you sold 75% of a million dollar company for 1/3 of the value. Is there a reason for that? For example, if you’re close friends with the investor you and the investor may be able to figure out a way to get the patent, defend it from the CTO and roll out a totally new company.