This "enterprise grade" terminology is suspicious. Did this CTO come up with that as a way to sell his value?
Too often in our industry the word "enterprise" is a smokescreen. Did he bring some real value to the table in terms of what the customer is seeing, or just some basic good development practices sprinkled with magic "enterprise" fairy dust?
Regardless, I have to agree with the other commenters. This guy is not your friend, he is not being straight with you, and he is not looking out for your interests. He could be a massive sociopath asshole, or maybe just an aggressive alpha nerd who doesn't know how to deal with personal problems.
Make sure you're protected. Your equity and your relationship with your cofounder are the two most important things to get covered against this guy, in that order.