Sorry about how you found out. Just a note and a wifeless house.
Her age and the boys going to college does point to some life transition turmoil. Perhaps it is not a full blown crisis, perhaps it is. Your response is the same - time and space for her; focus on you and the boys.
You mentioned that you feel she was troubled with S18 going off to college. Is he the first child to leave? Where is S20?
Looking back to the 18 to 24 month prior to BD did W show any signs of confusion, emotional reactions and stresses, etc...? These are very hard to spot while living with them. The progress to an emotional crisis or a lesser break is gradual and easily missed.
Contrary to how it appeared to you, her leaving was probably not a snap last minute decision. She had been going down this road for a while. If you look you will most likely see those little changes in her over the last year or so.
A caution for you. Do not re-write your history. This is two pronged advice.
Sometimes we will see or think we see things, and change our views of our past lives to make those pieces fit. This is usually towards making our remembered R worse than it was. Like suddenly you feel your W was a narcissist all along.
The other caution is the rose coloured glasses we all wear for the first while. One remembers things better than they really were and our history is alter towards the “it was a great R” side of things.
You are correct, this is a devastating time for you and the boys. Do not demonize W nor place her upon a pedestal - focus on you.
It takes time to find detachment and for one’s mind and heart to calm. As this slowly happens, you will remember things, real things, places, events, feelings, etc... Be accurate in thought and heart.
You have the gift of time, use it well. Look to yourself and become the best possible version of you.
As for a possible divorce. Good on you for seeing a lawyer. You are correct in getting information and learning your rights. Do not share what you have learnt with W nor tell her about your visits with a L. You need not push anything, just be ready for if she does. Treat this as a business deal gone sideways, for that is really what this part is.
The other side of your situation is not emotionless business. It is you and your boy’s healing. It is your choice to stand. It is realizing the path you have been forced upon. It takes time. And it is very rewarding.
Hope to talk soon.
DnJ
Feelings are fleeting. Be better, not bitter. Love the person, forgive the sin.