I think you need to go easy on yourself - those with addictions, and those ACs who aren't happy with their lives (for whatever reason) often try to shift the blame onto their parents.
My youngest step-son (mid 40's) is addicted to alcohol and gambling. We had 18 years of him bouncing us in and out of estrangement, simply because we wouldn't meet his endless financial demands to subsidise his poor life choices.
He then resorted to endless threatening, demanding, abusive texts and messages.
Even when my DH was desperately ill in hospital, he sent endless texts demanding money and (to top it all) demanding to know what was in the Will if he died...😗
Luckily enough, I'd already bought the phone home as my DH was unconscious and I was concerned in case it got lost/stolen.
I took screen shots, and wiped the texts before I gave DH back the phone - it was weeks later before I showed him.
There was no childhood traumas of divorce etc., - he was married with a family of his own before DH split with his ex.
He once said to me (and I quote) that we both needed to remember that "a child is for life, not just for Christmas"....what can you say to that? 🙄
Finally, DH told him he no longer wanted to know him. We still get the odd abusive texts, but we just delete and ignore.
It has upset DH a great deal. He feels that you always love your children, regardless of how they believe, as blood is thicker than water.
But, we cannot and will not, subsidise alcohol or gambling abuse, so there's no compromise to be had.
If step-son ever sorts himself out, then that might be different, but I can't see it happening, and his dad isn't getting any younger.
It's sad all round when children turn out this way as adults, but we are all responsible for our own adult lives, and can't keep blaming others.
Just protect yourself, and live the best life you can. There is no point in anyone being in your life who makes you unhappy or feeling threatened.
Best wishes. 💐