It’s interesting that our sons are from familys where their biologically dad isnt around, my ex has never been around properly for him but my husband is and even by my sons admission a great stepdad but I think the rejection from his real dad has a massive part to play in his issues.
Unlike u though my son was only 18mnths when we split I think he feels the odd child out as both me and his dad have remarried and have other children.
My son did go to the assessment I’ve heard but u dodnt know how it went and doubt I’ll find out.
I’m feeling crap today about things but do feel we had bo choice with everything that’s gone on and having to consider my youngest.
You son was a fully grown adult before your relationship he cant blame your partner ultimately hes has made the choice to take drugs and needs to take personal responsibility for that. All they seem to do is throw blame on other people. I had a very unsettled upbringing but I always stayed on the right path it is a choice.