I’m sorry noone’s replied, so here I am on July 17th. He is using and is clearly heavily addicted. The wisest thing is for you to go and see Women’s Aid and see how they can help you and your son (although as an 18 year old he’s now an adult.) As you don’t work, it’s likely that you can stay in your home while he will have to move.
(Realistically, even moving out doesn’t guarantee your partner will change/quit. Addiction is a horrible and selfish disease. Many don’t have the capacity for empathy, as they’re too busy thinking about their next hit.) My younger brother misused drugs most of his life but we had early childhood trauma, so I understood the reasons for using, and as he lived 30 miles away, I didn’t – happily – have to witness it. We met up every 2-3 months for walks and sometimes lunch. I paid a few of his bills the last 5 years of his life, but never gave him cash.
Have you got family close by who can help in some way. You have rights, so get the best possible legal advice – and Women’s Aid advice – you can. Sending hugs and strength to you! Fight for you and your son and don’t look back. It’s not your fault, btw. It’s trauma, not anyone’s fault.