Maybe the healing is just beginning? So your username is very appropriate!
Setting boundaries isn't necessarily comfortable. Taking care of yourself as a priority might not come naturally to you (yet). I think it is perhaps unrealistic to think it will, although it can become the norm pretty quickly.
I think it's especially hard to get comfortable with it if you have a person or persons around you that are used to you being self-sacrificing. It sounds like you are used to being and now you are moving away from that, looking after yourself and hey, you were this great caregiver and now you aren't! What is your role here anyway?
I have completely abandoned him
I even feel guilty for making him fend for himself
If this were read out of context, I would think you were talking about a child or a puppy.
But you're not. How old is your Husband? Are you responsible for him or is he responsible for himself?
That's where the guilt is. You somehow think you are responsible for him. Why is that?
Regardless, perhaps it's time to shift the focus on to yourself and your teenagers, they need you much more than he does. You need you much more than he does! You are not the world's caretaker.