I don't know what to do anymore 😔

My son turned 10 in April. He's always had a problem with authority, has wanted to do only what HE wants to do, yet expects everyone to do everything FOR him (something I've never allowed since I believe in learning by doing). He has also been an arguer. But since he's turned 10 it has been worse than ever. If he doesn't get his way HE CRIES! So hard that his shoulders bounce up and down!! If he doesn't want to do something he is instructed to do HE CRIES! If I tell him to do something he says "okay" and then doesn't do it. So, I remind him of what he was instructed to do and he'll say "oh I forgot" and not do it STILL. So when I go and remind him a third time, I'm irritated and escort him to do whatever it is that needs to be done and stand there while he does it (if I don't, he will pretend to do it or not do it and lie). The most irritating thing that he is doing now is when I tell him to do something and he responds with a "No, But-" sentence. Like we are having a discussion! Me telling you to brush your teeth: not up for discussion. Me telling you to shower: not up for discussion. Me telling you to do your homework: not up for discussion. You know, things that he has done routinely for the last 5 years he's been in school. "No but I just wanted to do blah blah blah first" "No but why can't I just blah blah blah and then do my homework" "No but I hadn't planned on doing that right now." EVERYTHING I INSTRUCT HIM TO DO HE STARTS HIS SENTENCE OFF WITH "NO" and I am soooooooo over it already. He has a written timed out schedule. One that was suggested we do by his psychiatrist to help with his ADHD. He's had this same schedule (one for AM & one for PM) written and hung up right by his dresser where it's obvious to see) When he gets off task, I make him recite either the AM or PM schedule to me. He knows both by heart. I asked him why he has to be reminded and told what to do CONSTANTLY if he can remember everything he needs to do and you know what the little turd said?? He said "bc I don't want y'all thinking I'm responsible bc then I'll be expected to do stuff myself and I just want to be lazy and see what I can get away with not doing." Omg i was HEATED. He says it's bc when he goes to his grandparents house (Thursday afternoon til Sunday evening, not court mandated) he doesn't have to do like anything. He doesn't have to make his own bed bc he shares his bed with his dad. He doesn't have to bring the trash can back to the house. He doesn't have to brush his teeth at night. He isn't made to comb his hair after his shower so it dries knotted and messy. He isn't allowed to play/sign up for sports or physical activities bc they'll take time away from hanging out with his dad, He isn't made to use manners like "yes/no ma'am/sir, please, thank you, may I please, will you please, etc", they let him eat a whole large pizza by hisself EVERY WEEKEND, they don't make him eat veggies bc he doesn't "like" them, they don't let him pour his own drink or milk in his own cereal WHICH HE DEFINITELY CAN DO... the list goes on. He comes back argumentative, disobedient, disrespectful... its like he needs to be reprogrammed every time he comes home. We've tried reward system, taking things away, money rewards, groundings, time outs, lecturing... we don't spank. Not really bc I didn't think he needed one at times but bc I've never been able to (as I was a single parent until 3 years ago) and being 115lbs at 4'11", he's been almost the same size as me since he was 6 (now he's 5'2" and 126lbs) so I was never able to. I need suggestions on how to get him out of being so argumentative and disrespectful. It takes all my strength not to smack him across the face when he gets and attitude up in mine. My husband can't stand it either and blames my sons dad bc he acts more like a buddy or brother than a dad. I hate raising my voice to him so much I feel so mean. I hate having to physically take him to what he needs to be doing bc he always says "you can't just grab people like that" or "you can't just force me to go somewhere like that." I don't even grab him hard! I have to sometimes push him with my body to go brush his teeth and he resists by pushing back on me. And threatening to tell on me to another grown up like I'm some child who is bullying him and peer pressuring him... I'm at my wits end... I'm doing all I can to raise him right... I feel like such a horrible mother... I'm failing him... he's going to end up not knowing how to anything for his self despite my best efforts...Â