Darlin I'm so sorry. Please dont cry - we all have something in our genes that we're predisposed to but that doesnt mean we have to carry it on and it doesnt mean that your son will. My daughter is also genetically proned to addiction but she is the polar opposite of her brother - more like me. Not saying that I could have stopped my son's addiction but had I known then what I know now - i probably would have done quite a few things differently. Here's a few things i think I could have done better:
I would not have been so free spirited with my son and I would have spent more time talking to him about things like solving your problems in healthy ways.
I would been more insistant that he play team sports (which teaches kids how to work together and think about others).
I wouldnt have said stupid things to him like "pot's not so bad."
I would have gotten him the help he needed when he was young to deal with the issues instead of waiting till he had full blown depression - he would have still dealt with it but may have not taken it to such dangerous levels just seeking attention.
I would have been his parent and not his friend.
More than anything - I would have enforced consequences everytime instead of letting him off the hook all the time. that was the one thing that i did teach him that he struggles the hardest with - he knows how to talk his way out of anything.