You probably are not going to like what I have to say, but here it is. I think first thing you may want to consider is that your husband may be a pedophile. It is not normal for a grown man to be infatuated with a 16 year old. I think he needs counseling NO MATTER WHAT ELSE HAPPENS.
No wonder you are having problems with depression. You have every right to be depressed. It sounds like your husband is attempting to place the blame on anything other than himself. If he felt like you were not giving him what he needed, it was up to him to let you know, not take it to a child. This sounds like a serious ordeal you are having to deal with, and if you are not in some type of therapy, you need to get there.
By him not accepting blame, means he probably doesn't see any wrong he has done in doing what he has done, and I would wager what he has done is close to illegal, much less breaking his vow to you. The two of you need to get into some sort of counseling, by your selves, as well as together. Again, like the good doctor says, you can't change what you don't acknowledge, and it doesn't sound like your husband is acknowledging any wrong doing. I think there is danger of him repeating his behavior, without acknowledging wrong doing, as well as intervention.
Right now you need to focus on you, and getting your self back into harmony with your world. With your husband acting the way he has been acting, your children need a sound and reasonable parent, and it will be tough to be that anchor for them, with having to fight depression. I don't know if you have talked to your doctor about your depression, but you need to if you have not. There are lots of great medications out there to help in this area. I am a Vietnam veteran, and when 9-11 happened I had to go on Paxil, an antidepressant, for about six months as I had felt I had already dealt with my hell, and at my age I didn't think I would ever have to deal with such tragedies again. I was so thankful for the medication, and I had no shame in taking it.
Some people have to be on medication for depression the rest of their lives, and I look at it as no different than a diabetic needing their insulin. I am not a trained professional, and whether you take my advice is totally a choice, but what I feel you need to do is this: Get into therapy, and if hubby doesn't think he needs to get into therapy, ditch him before you wind up losing everything paying his legal bills as well as a civil lawsuit from the next 16 year old. Talk to your family doctor about how he/she feels about you taking some sort of anti depression meds for at least the time being. Focus on you and your children, they are what truly matters, husbands are a dime a dozen, and I bet you could get two dozen like yours.
What happened to you and your family is not your fault, and you own nothing of your husband's behavior. It was his choice, not yours. Blaming you for his behavior without him attempting to talk things out with you is just as insane as him turning to a 16 year old . This is something he needs to own up to, not you.
These boards are a wealth of information, and a great place to be able to have a support group. Other boards you may want to read are the "Cheated On" and Infidelity boards. I hope this has helped. Good luck, and keep us posted as to how you are doing, as well as how things are improving in your life. I will have a good thought for you, for what it's worth.