Teach, you are right, it most likely will get worse before it gets better. It will also take a long time. Just keep validating and GALing.
Have you sat down to talk to your son about what is going on? Sitting down with him and asking if he has any questions or thoughts that he might want to talk about is important. Then, no matter what happens with your H, your s knows you are around for him always.
Your sitch is close to mine in that my H first told me that he was unhappy, but wasn't leaving or talking about D yet. Two weeks later, he told me that he wants a D.
I focus on myself and my S and it helps tremendously.
You're doing well and will come out of this one day.
{{hugs}}
M 46 / H 43 T 24/M 18 S 4 11/6/2014 ILYBNILWY 1/16/2015 Living in separate bedroom 1/8/2016 H moved out