You two have been through a lot. None the less, you have stayed together for 17 years. That’s reason enough to try to salvage the relationship.
I don’t think your wife is correct. Regardless of her perception that she has been able to cope with her past, it is likely that her mood swings and her difficulties with sexual intimacy are connected to the childhood abuse.
Ironically, sometimes a person with a history of abuse knows how to deal with sex with someone who doesn’t matter but can’t be intimate with someone who is loving. She may fear that the circumstances of abuse will happen again — where someone who supposedly loved her hurt her.
Your wife’s therapist can’t get to the root of her anger and mood swings without knowing her entire history. It’s understandable if it is easier for your wife to talk about your infidelity than what happened to her as a child. Thinking about revisiting that history of abuse may be terrifying. But I do think it is important for her to do just that if she is to have a loving, intimate relationship with anyone. Her therapist should know how to help her feel safe and supported while she does that therapeutic work.
If any couple needs couples counseling it is the two of you. Clearly, there is much to talk about but you two may not know how to do so without triggering her anger and your guilt. A couples counselor can help you both understand what has gone on for each of you that you haven’t been able to be the kind of partners you both want and can help you learn better ways to be supportive of each other. Further, a counselor can provide a safe place where you can bring your hopes and fears.
I wish you both well.