Wow - he's only 12? He's crying out for discipline and boundaries. Kids need to know there are hard and fast rules - they need their parent(s) to be a parent. How difficult for you as a single mom - and I also assume a mom who doesn't have great self-esteem. Your son needs someone - probably another man - to be the discipline that he so badly needs. I am not talking about "punishment" - I'm talking about learning the disciplines of life - working hard, taking responsibilitiy for actions, planning ahead, consequences - both good and bad of our actions. Young men seem to respond so much better to adult men - is there no one in your life like a brother, uncle, etc who can help you in this regard?
It seems that he's lost respect for you completely and I don't imagine that you'd be able to turn this ship around quickly - he needs this quickly. If you know of a good boarding school and you can afford it - then it might be the thing you need to do. It will be tough - oh my goodness I can't imagine. BUT - until about age 22 that his brain and emotions are still pliable and resiliant. He can relearn how to operate in life / society. He can learn to be a man. AFter age 22 - 25 the brain has pretty much developed and it's much more tough to re-learn things. All kinds of brain studies using PET scans and such have shown us this in the last 5-10 years.
Expect that he will be VERY resistant. Expect that he's going to resent you - at first. Eventually he'll realize you did this for his own good - but he won't go without first putting up a huge battle. Expect it so it won't surprise you soften your intent..
I have a 14 yr old daughter and an 11 yr old son. This is what I know - they will rebel, they will act like they want to be running their life - but they feel a sense of security having boundaries. When they do something to lose privileges and we have to discipline them the may get really upset, slam a door, say that they hate us - or that we're the meanest parents ever - but after the "storm" they seem to take this huge, contented emotional sigh - as if they are at peace knowing that they have someone else in control and reigning them in. They are really scared to death about running thier own life and they want the security of knowing there's an adult who will ultimately stop them from making huge, scary mistakes and will protect them. My daughter will complain that we're too strict, we're the worst parents in the high school, that we don't let her do anything - but when pushed she will admit that deep deep deep deep down she's happy that she has hard & fast limits.
If you can't get the limits set up and instill them then someone needs to. Listen, you may get him off to boarding school now - and get yourself into parenting classes, or counseling and in a year or two he may be able to come home and the two of you can re-build your life - with him following rules, helping around the home & being respectful.
Pray for guidance mama. We have a God that really does care about the details of our life and wants the best for us. Praying for you D..