I'm sorry he is doing this to you, but try not to let him. He wants drugs. You know that. He is crying and begging because he needs money for them and if he came home he'd probably steal from you and/or abuse you and your little five year old doesn't need that in her environment. I would unfriend him. Why read his FB? If he is writing posts just to upset you, there is no point. Nor do you because you are also important. Your little one needs a sane, strong, healthy mother who looks after herself and does not try to change her oldest son who is now a man and will only change if he wants to change. On the street, everyone knows where to go for food, rest, help. It is a community. The only thing that he may not be able to get are drugs. And drugs are why he can't get a job...if he is even looking. Would you hire a young adult who couldn't pass a drug screen if you had a job to fill? Until he decides to quit, his life will be this way.
I agree he sounds like he is hitting rock bottom. Crossing fingers, toes, and eyes...but try to focus on YOU today and stay away from Facebook. He is creating drama for you through his posts. He knows you read them. Nothing gained by being his captive audience. It just hurts you, doesn't help him. Is he calling you too? Texting? If it were me, I wouldn't answer other than to tell hm you will talk to him later, when he is sober, calm and pleasant. Then I'd stick to it. In fact, I did that with my 36 year old son. If he wants to talk to me, he has to talk to me the same way I do him. And he can't ask me for anything. I'll be happy to talk to him, but not if he is hysterical, threatening suicide, abusive and/or demanding of money or other comforts. Then I hang up and won't answer for a few days. He is much nicer these days.
Hugs for your hurting mommy heart.