In my opinion, your reason for not wanting to do individual therapy first and separately is a little controlling. I know it's out of anxiety. Seeing how your partner acts on their own accord and not because you're forcing them to do something is very important information. If he does stop going to individual therapy, it's not your role to force him to start again. It's your role to assess what that means about the relationship and maybe even how much respect he's willing to give you and your wishes

Wait you're a young woman who dates older guys... Who is surprised by older guys she dates being attracted to young women?

You're trying to make a crappy situation make logical sense when it doesn't. This man does not want to be with you. You might even want to make sure he's not hoping to be with someone else.

I know you asked people to be kind so I won't pile on, but the other two commenters are absolutely right. This man is not ready for marriage, it's more like you are playing marriage (and he's not) than actually acting like a married couple.

He's in a situation where he can live how he likes and barely works and openly disrespects you. He's not a man of strong character by the sounds of it, so only a negative consequence will change his behavior if he ever changes. Clearly love for you and your children isn't enough to make him step up and be a present father and husband. You can impose a negative consequence by leaving for a few weeks until he changes his routine.

I'm confused as to who is going to work to pay the bills for your babies?