He is living in his truck because that is HIS choice and has absolutely NOTHING TO DO WITH YOU. You are not a bitch. You did not cause him to use. He is living in his truck because he squandered the savings he had on drugs. He had $3,000 saved up. He is capable of saving that much money again if he stops using drugs. Don't give him gas money. Don't give him money for a place to stay. You owe him nothing.
In a time machine kind of world, I wish that I had said as much to myself when my addicted husband was badgering me for money for gas and a place to stay. I kicked him out at one point. He didn't have the money for gas or a roof over his head. But you know what? He sure could spend $500 on drugs pretty darn quickly without blinking. And being verbally abusive when I didn't give him what he wanted. And that is exactly what all your guy's name calling is. Abuse.
Take care of you.