I think its great that your son is still into lacrosse and also hits the gym. My friends and I got into marijuana in high school and I think being on various basketball teams warded off taking it to the next level for me.
My oldest, almost 17, is also really into basketball and I'm grateful for that because he also has a few friends that may not be the best influences.
He rarely discusses anything about my stbx with me. He seems to have accepted her abandoning(IMO) us and seems unphased by the current state of their relationship but I know deep down he has to have some buried feelings.
I've struggled since this began to walk the rope of sharing enough vs. sharing too much and I still have regrets and doubt if I'm handling this the right way with him and my younger two.
Of course you want to do anything in your power to help benefit him and I see you hurting and searching to find those answers.
This experience is having a major part in the develpment of them as people for the rest of their lives and I hope somehow the positives will outweigh the negatives.
Thanks for sharing all your insights and interactions because I know it is helpful to a lot of us.