I don't know that either of you did anything "wrong". Perhaps, based upon all of the things he's done for you when you needed him, you set him up to be more than he was.

His conditions for getting engaged are not unreasonable. But it sounds like he doesn't want to be in this relationship, even moved on, but is really insecure about how to end the relationship.

I fully understand that you don't want to disrupt the lives of your children, but don't you think they deserve a stable, predictable home? Kids are more perceptive than we give them credit for.

It also sounds like you jumped into this relationship relatively quickly. When we end a difficult relationship we aren't always seeing things clearly.