I posted upthread about separating the 2 issues, school and behaviour, but you have them all tangled together in a mess.
Back off on school work. Seriously. and don't just randomly stop, but sit down with ds. Tell him youhave been thinking, and you'd liek to try a different approach. Tell him that school work is between him and school. If school are asking him, and he doesn't do it, and school isn't imposing consequences, wel, then he has zero incentive to work, and I don't blame him.
My ds did almost nothing after GCSEs. I would have loved him to do something constructive, but he didn't. Then in September he got himself a Saturday job and pulled his finger out and started working.
So, calmly tell him that school work at the moment is between him and school.
Second. The X-box. To be honest? if staying on the X-box for hours is his way of coping with lock down, well, it won't kill him. So, in that calm conversation, I would throw it back to him. He is 16, you are going to let him decide how he spends his time, with a couple of rule sin place (see below) but you expect consideration, eg quiet when you go to bed. 10pm is very early. Teen all play at night, so you are cutting him off from his friends. The better way may be to say you aren't allowed on unitil 2pm if you want to limit time.
Third the phone. Well you took this away because he swore at you and was vile.
This to me is the key issue. Don't tie it up with the school work and x-box. This is the place where I would be firm. So, I would say - you swore at me. This is my home and I don't expect to be sworn at in my own home. You are 16. I don't swear at you, you don't swear at me. When you treat me with such rudeness and lack of respect, then I will remove something, x-box/phone/wi-fi etc. If you want me to treat you like an adult, then behave like one, in this area that means no swearing, no foulness towards me. I would put a time on the phone being removed eg 1 week. Only returned if he is not being rude/swearing.
Then the basics of the family are that he does one (or two) helpful job per day (I have a list for my kids so they can choose). You could add a couple of weekly jobs on (mine are cooking once a week at the moment). Acknowledge that he is moving towards adulthood, that things will change but as part of that comes responsibility. Jobs.
If the jobs dont get done, then either turn off the wi-fi, or don;t do something he wants, eg cook him dinner (be carefful though, if he can cook himself a pizza from the freezer, he might not care)
Sorry htis is long, but you need to let go of sone things, and be zero tolerance on others. At the moment it feels as if you want tight control of all of them