If you were on a ship and it was sinking, who would you save? Your 2 older daughters who are adults and have had or have taken everything they could get and then treated you badly?
Or your 15 year old son, who is a child, still an innocent on a good path and deserving of all the good parenting you have to offer?
All the drama and chaos your older daughters love to live in and draw you into steals the time, energy, and loving mothering that you could be giving to your son. And to yourself.
Many years ago when my children were young, I read a parenting book that had a chapter about dinosaurs. That seemed irrelevant to me until the author explained. He said "treat a child's bad behavior like a dinosaur. Starve it for attention, and, like the dinosaur, it will go extinct".
Your son will blossom with your love and attention.
ShootingStar1