I'm glad you are going to receive the therapy you need. Maybe working with them you can figure out a way to make it all work out. I'm still sorry that you're even having to put up with this.
Don't get too upset over the option to "break our family apart". Your kids are young right now, so they won't know, but coming from me (someone who grew up in a semi-similar environment) I wish my parents would've divorced a long time before they actually did. You're not letting him down, he's let you down by forcing you to have to make this decision for the sake of your kids. Don't pin undeserved blame upon yourself like that; your husband should've grown up enough to care for his wife and kids.
With enough work, this can get better; it's going to be hard as hell, but worth it.