Most Helpful Guy
First of all, what self-respecting woman would stay with a guy who treats her like that? If you both just wanted sex and that was it, that's fine, but you want more and he doesn't. He outright told you he didn't want a relationship, but you stayed anyway, even after he started sleeping around. Even worse, you introduced your kids to him, even though the chances of him ever being their step-dad are close to zero.
Bottom line, this is a big mess. You're not just hurting yourself by staying in this situation; you're also hurting your kids. There is nothing inconsistent about him liking you AND seeing you as a FWB. If you want a committed relationship with the potential for marriage down the road, this isn't the guy for you.