That is an EXCELLENT reason to leave. And in time he may wake up to the reality and decide he wants to change for himself.,... to no longer be the person he was becoming.
But I wouldn't set your hopes and dreams on that. As said above , I would be working on what you need to do for you and your child/ren first and foremost.
I would be speaking to a lawyer ( even if you don't hire them ) to get their advice on how to proceed.
There are many different caveats in law and it can be a very painful drawn out process and at least having the information is the power to decide how you want to handle things going forward.