Good morning all!
User101 I'm so sorry that you feel so
right now - it all sounds really hard - and even worse that you feel alone with it all.
Rest assured you can come on here and vent any time.
In the often quoted Mumsnet phrase, it sounds like you have a dh problem as much as there is a teen issue here (which sounds like a pretty "normal" teen rebellion to me). My dd is the same age as your ds and she is only doing school work because her school (not in UK) have made the children sit three exams in their three weakest subjects so that they have to keep it engaging until the end of term. If it wasn't for that, I don't think she would be doing that much study tbh and anyway, all school work stops in a couple of days.
Fwiw, I would say, first of all, cut yourself some slack, we are in the midst of a global pandemic and it is an unprecedented situation. Everyone is feeling the strain. Also, you cannot help the cultural differences that inform your dh's perspective. Finally, it is really unpleasant to be piggy in the middle between two opposing factions. You are not responsible for any of that and you shouldn't have to be the one that constantly suffers because of it.
[Btw, how do your dh and ds get on when you are not in the house? Do you have any other dc? Three is a difficult number sometimes! ]
So if I could (I have no idea if this is correct advice or not mind you) I think I would call a family meeting and make it very clear that this can't continue and you are not going to engage with their arguments any more seeing the two people you love the most in the world at odds is causing you too much grief and stress. Then I would try and step back, withdraw as much as possible, and get on with your own projects. Don't allow yourself to get drawn in or involved in any arguments. Keep cool and calm and aloof. Say you will only engage with them both if they are civil to one another. Are there any activities you could do all together that you would enjoy to try and alter the mood a little bit?
Then I would take your dh away from the house somewhere and make it clear that his reaction to a child being home 45 mins later than planned (personally I think a curfew of 9pm for a sixteen year old who doesn't have school the next day quite harsh) isn't great but maybe the time that he required your ds to be back home was a little early? Remind him that parenting isn't about rules so much as a relationship.
Then could you ask your dh about his relationship with his own parents. What were his perceptions of his parents as a child and then a teen? What are his expectations of his son? Would he be willing to engage in a parenting course or just take his son out occasionally to do something together they both enjoy to get their relationship back on an even footing?
Good luck User010 it all sounds really difficult
Can you ringfence some time just for yourself to day to go out and get some peace for yourself?
Thanks for your lovely comment ttwillpass (especially when I thought I was being quite moany
). Thank you so much for that link. It is really helpful. Especially the bit about it HELPING a child if their parents fail him or her in a few minor ways now and then as "that's life" and it allows them to develop resilience. I will keep that in mind!
I received a very nice letter from dd the other day apologising for being so horrible which was surprisingly reflective and I must admit I feel hugely better for reading it. Unbeknown to me (because she hadn't said!) she had already been making plans for the summer/her birthday and she misunderstood the plans that I was suggesting. Essentially we were both aiming for the same thing but had misinterpreted each other. It just shows how communication can go badly wrong when two people are hurt and angry with one another.
Welcome to the thread ComplexNeeds I'm really sorry to hear about your dd self-harming. You must be so worried about her.
.
That's an especially really tricky situatiion when you have heard through a third party too. Did you see the link posted below about self-harming from Young Minds? Here it is again here. As for the withdrawing, I think that is a pretty normal part of teen life for some adolescents. They are preparing themselves for independence and a safe first step, is to isolate in their bedrooms, so I wouldn't worry about that too much. Obviously, it's very difficult though when you are not able to communicate. Could you take her on a drive or engage her in an activity where you are alongside one another (not facing each other directly) so that it is easier to speak? Good luck 
Andi good luck with sorting out truth from fiction!!
This article here is quite interesting about adolescents lying. A lot of it is about establishing autonomy and engaging in a world that is separate to us I think. My dd doesn't lie but there again she doesn't tell us much about what is going on at the time at all! She only get to hear about it months/years afterwards! It is a bit scary I must admit.
Take care everyone! Remember to try and take some time out for yourselves if at all possible.