I can't take it anymore

Well, eventually he will have to take responsibility or he will keep losing priveleges. Maybe try setting a short-term goal that is realistic for him, fairly easy to achieve, so he can see a reward for good behavior. Then slowly increase the difficulty.

He's saying those things because he's mad and wants to hurt you and/or get you to back down. I'm pretty sure he knows it's his own fault but he's mad. You have to stay strong and decide you're not going to let his ranting get to you.

As for me and my parenting style, I don't stand for fits. We all have a right to be sad/mad/frustrated/angry but we don't have a right to take those feelings out on anyone else. If my son wants to mouth off like that, yell, scream, whatever, he goes to his room until he's done and calmed down. If going to his room is not an option, then we start adding days to his grounding and as soon as we get home they go on the calendar. He does not get away with disrespecting me or anyone else.

Listen, I know it's not easy. You have the hardest job on earth and you're doing the best you can with what you know. These little stinkers don't come with instruction manuals. I'm just giving you bits of info from my own experience and maybe there will be something you can use. If not, at least know there's one more person supporting you.

Sounds like we are very similar. I do the same thing, I don't put up with backtalking/giving me attitude/throwing fits. I too send him to his room, which always turns into a huge powerstrugge, because he just refuses to go until I drag him off. And I too keep adding days to him being grounded and write them on the calendar. As for rewards, we have a reward chart, my son gets points for good behavior, helping out, and so on, and he loses points for things like arguing or getting in trouble in school. If he has 50 points at the end of the week, he gets a special treat of some sort. When we first started this, he usually had the 50 points by wednesday. Now he doesn't reach them at all anymore.

Well, it sounds like you're doing everything you can at this point. Just wait until he gets on some meds that work. You'll see a major improvement.

Meanwhile, do you also have him on an IEP at school? If not, he should be. There are a lot of things available with an IEP in place. We can chat about that anytime. Both my kiddos are on IEP's and it has helped immensely to work closely with teachers and counselors at school. I ride them close, too, email and call at least a few times a week. I'll warn his teacher in the morning if he's not feeling well, has a bad morning or looks like he might be out of sorts, so she can be ready to give him a little extra help if needed. I also let the teachers know what rewards or consequences are in place for him at home so they can support him to achieve those things.

Hang in there, sister. It's a process but you will see success and all your hard work and perseverance will pay off for your son. All good thoughts and prayers for you!