Beanner, I have been where you are. When my son was 13-14, I could not say anything to him without him taking offense. Even good morning or hello were offensive to him. He said the most awful things to me that you could imagine. Not just cursing, he was vastly more creative than that. He said things designed to destroy my self esteem and my enjoyment of any and everything. He was great at it. He was also incredibly violent. It was so bad that we moved him to my parents house a few miles away. I couldn't even see him for a few months. Mostly because he flat out refused to participate in anything I was at, even family meals. It broke my heart. I then had a breakdown, a physical one where my body just mostly stopped working and every movement hurt. My doctors said it was from stress making two of my illnesses go into hyperdrive. It has been 9 years and I am still dealing with some of the problems.
The good thing is that I have my son back. He is almost 26 now. He has his own apartment, recognizes how awful he was and is incredibly hard on himself over it. I just want him to forgive himself and move on. He is wonderful to us. He is an involved big brother and he is always willing to help out if we need him. This is something that I NEVER could have dreamed would happen back when he was younger. Even when he was 18 it was a pipe dream. We even have game nights where he comes over and we order pizza and play something like Cards Against Humanity. It is incredible to have him with us.
So don't give up. You may have to take a break or let someone else step in. You have to get on the same page with your husband. I was the mean parent also, the way you are. Get your husband to stop just saying yes right off the bat and start asking about the chores first. He knows your son doesn't do his chores. Make a board where you write down what you asked your son to do and you initial if he did it. Or something like that. Sure, you do it with little kids, but you can do it with older ones too. Make your husband start using that to see if your son can do something.
And as far as that "I will go to php if I can go to friend's house now" stuff? That is bovine excrement. You need to be on a Do to Get system, not a Get to Do system. He wants to get to go to his friends house and then he will do what you want (go to php). That is not an acceptable deal. He can go to his friend's house AFTER he goes to php. Otherwise you and I and the dog all know he is going to refuse to go to php when it is time. Change the system so that he has to EARN the reward before he gets it. Do to Get. It works.
Also stop thinking about consequences as you handing them out. You are misunderstanding the system. You are not handing out consequences. He is earning them. He is CHOOSING to have consequences. You are not the one in power, HE is the one in power. He can avoid the negative consequences and get only positive things. How? By doing the things he is supposed to do. By cleaning his room, getting good grades, not being disrespectful. By acting poorly, he is choosing negative consequences. Explain that this is how the world works. We ALL, every single person on the planet, choose our consequences. If we do good things, we get good rewards. If we do bad things, we get bad rewards. It is not Mom being mean or power crazy, it is LIFE. Better he learn this now.
By the way, have you drug tested him? You don't know that he isn't using unless you drug test him. Buy a test that covers as many things as possible, and then test him when he comes in from a friends. Do NOT give him any warning or let him know you have the kit ahead of time. Do have your husband watch him pee. No, your husband won't like it. It is a consequence of a having a misbehaving teen. The drop in grades, change in behavior, etc... are all classic signs of drug use. Don't trust that you will see signs around the house. Drug test him as soon as he comes in from being out with his friends, preferably on a weekend when they are more likely to party. He won't like it and will be angry. Ignore his ranting. Do it anyway and don't let him talk you out of it or bargain this or that if it is clean. If he does that, he may be using something your test doesn't cover. But the most comprehensive multi-panel test is the best bet you have to figure out the truth for this question. It is what the doctors offices use generally.
As you do these things, also do nice things for you. Don't forget to care for yourself. Date nights, bubble baths, good books, music, whatever relaxes and recharges you. If you don't care for yourself, you cannot care for anyone else under any circumstances. This is incredibly important!!! Make sure your hubby does the same.