S, I'm very sorry to read that your marriage is tumbling down the hill very fast these days and a divorce is right around the corner. Once they start the ball rolling, it's a fast moving one. The only advice I can offer you is to listen to your lawyer, answer the questions as truthfully as you can and look at this as a business arrangement gone sour. It's no longer a warm and fuzzy relationship, but one that's gone sour.
The ow is most likely behind a lot of this. They tend to fill the spouses (who are very weak at this time) with ideas that we'll take them to the cleaners, we'll punish them and the h's have to beat us to the punch. They think the ow is there for them, but what she's looking for is a good time, plenty of money and new security w/our xhs.
Once the divorce is over and done with, it takes about 6 months to even a year or so and the euphoria of that new found freedom will tarnish and he'll begin to realize just what he's done. Will he admit it? Probably not if he's got a lot of pride.
As for you and your son, you are going to be okay. You've managed thus far and believe me, once this is behind you, that heavy old monkey will be off your back and you just may be surprised at how well you feel (health wise). S, I'm not saying it's going to be easy, but in time, things will settle down and you'll develop your own routine, which will not be dependent upon your h.
No matter what, protect yourself and your assets. Fight for what you feel is a fair and just settlement for you and your son. If your h isn't happy at the end of the day w/the settlement, too bad. You are to the one that stood by him through thick and thin. Let the ow now pick up the pieces and start over w/a man that hasn't been truthful w/her either.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.
