Ask HN: Advice for troubles with Co-founder/CEO?

Recently the relationship between my fellow co-founder (CEO) and myself (CTO) have hit very rough times. He asked me to take on the responsibility of managing the tech team. It was once just me, and we have grown to three. Now I have organized the Sprints and the development process, but he is constantly micromanaging me, and the rest of the team.

He is directly asking developers to work on small, meaningless projects during the sprint that cause us to lose time and focus. He even told me he knows it is not helping, but still refuses to stop doing it.

Additionally, he is now making all business decisions himself without even consulting with me. I own around 25% of the business and my stake is comparable with his. Before we would meet and discuss, and then come to a decision. I recently took a small vacation, and when I came back he had decided to throw out our revenue model. He also had been secretly raising a Series A and interviewing developers without my knowledge.

Once we raised our seed round, it seems that the power and thought of money has gone to his head. I am on the verge of quitting, but I have worked very hard and believe deeply in the product. I really am not sure what to do. I have confronted him multiple times, but he refuses to change or even communicate clearly.

Any advice would be greatly appreciated. I can provide further details if necessary.