Sorry this is so long! I submitted it to the website but I don't know if it will be answered, so basically if anyone has any insight on these issues or ANY advice, it would be GREATLY appreciated!

A few months ago, my mother reconnected with an ex boyfriend (from high school) on facebook. She was pretty open about the whole thing, even asking my father if it was okay if she friended him before she did. My father was fine with it, and she continued to talk to the guy.
A little bit later, my father accidentally discovered that she was posting things like "Hey baby" on this guy's page. This caused a huge argument, as my mother said that it was an invasion of her privacy and that it was no big deal, that it didn't mean anything. Eventually, my father was so angry about the situation, that he asked her to delete her ex boyfriend from facebook, which she did do.
More recently, I've noticed behavioral changes in my mother. We have always been very close and recently she seems distant and uninterested in the things I have to say. I go away to school, so the time that I can spend at home with my family during the summer is time that I cherish. In the past, I've felt that she felt the same way, by appreciating me and not taking the time we can spend together for granted. This summer, however, she often yells and screams about how she wants to be alone, how she is frustrated with my brother (he's 15) annoyed at my father, and when I try to talk to her about these behavioral changes, she just gets mad at me, telling me to not worry about her and to stop caring so much, often times, leaving the house after one of these outbursts, and comes back as though nothing has happened. One week she'll be down, another she'll be up. I feel like our relationship has suddenly become very touchy, as though I'm walking on eggshells around her erratic behavior. She's also been losing weight and getting back into drinking and smoking pot lately. She talks about getting plastic surgery. Because of these reasons, I believe my mother is going through a mid-life crisis.
To add even another layer to this awful tale, my father has grown more and more suspicious of my mother and her ex-boyfriend. (The ex doesn't live nearby so I do not believe they are having a physical affair, but I do think there are emotions involved.) My dad has started to snoop around her computer and see what she is doing. He has found that she created a separate e-mail and facebook account in order to talk to this guy. (Though as of right now, we don't know if she's actually been talking to him, just that she has attempted to.)
My father has been so distraught by this that he can't eat, can't sleep, and is getting distracted at work. Every time my father attempts to talk to my mother about the situation, she hardly says anything, and tells him that he has the right to be suspicious of her. My dad feels embarrassed by the situation, so he hasn't told anyone. Anyone except for me. He knows he shouldn't be snooping around her computer and he knows he shouldn't be talking to me about these things, just like I do. But I feel so horrible about the way my mother is treating him that I can't help but be there for him when he attempts to talk to me about it.
I've tried to talk to my mother about what I know and what is bothering me, and she has agreed to go to counseling. But my mother is a very stubborn person and has even said that she doesn't think the counseling will do anything. I think that is also very important to get my parents into marriage counseling, as there is obvious trust issues going on between them and to save their marriage through this tough time. (on top of whatever else is inside my mother's head.)
Basically, how can I convince my mother that she needs to go to marriage counseling with my father on top of her own counseling without spilling all the extra stuff that my dad has told me? (He has said to me that if it gets out that he's sharing these things with me that he's "dead") The prospect of my parents getting a divorce is already too much for my mind to handle as my parents have always such a good relationship until these recent changes. To add my mother leaving for another man makes it unbearable to think about, and I've been crying almost non-stop with it weighing on my mind. What am I supposed to do to make this okay in my head, and to prevent my mother's mid-life crisis and irrational behavior from ruining an otherwise fairly smooth 22 year marriage?
Also, I go back to school at the end of this month and I'm afraid of what is going to my family once I'm gone. I don't know what to do about that either! Help?