I am not saying you should end your marriage.
But your husband absolutely can live without you. That should be a reasons to stay. Sometimes it feels like we can't. But the vast majority of people do carry on living. If he is actually saying he would kill himself that's a whole other story and indicates emotional abuse.
You would also find a way to be a single parent. He would have to pay CMS to start with. And if he is so great, he wouldn't begrudge that.
Its mot way being a single parent. Neither is ending a marriage. But sometimes it is the better option.
You don't seem that invested in your marriage yourself. Your reasons for wanting the marriage to work, is because of the impact on him and that it will be difficult.
To save a struggling marriage, you need to want to save it, because you want to be in the marriage. Not because he does and not because otherwise it will be hard.
Again, I am not saying end your marriage. But I think you really need to think about things alot more. If your husband picks up he is more invested than you and then you go back to work, with this man. Your husband may not be be fine when it's happening.
Maybe you need 5o talk this out with someone, a trusted friend or counsellor or somebody.