Hi :)
Firstly, you need to have a chat with school and let them know to separate spellings and golden time, golden time is so important and their self esteem is easily knocked when they lose it. Could they use letters on paper to get DS to use those to spell the words or fridge magnets - they need to encourage him not punish him.
My DS is a pain with homework and it's on his my IEP (set by school) to do homework with him. They suggested using a pinger.
This week, I decided to do things differently and before we leave the house, I check and remember two spellings. On the walk to school, I ask him the spellings, we chat about word sounds and then when he can remember both of them, we chat about general stuff.
Okay, we also sing a couple of songs from Look and Read which is a fun way to keep phonics in his mind - and then we talk about general stuff.
The Look and Read episodes have been a lovely bonding thing for us over the last 2 weeks. We raced through three series but now are watching Badger Girl one episode a night before bed. If you're not familiar with them, they're a BBC program with a child-centered drama broken up with "intervals" of people who are "writing the story" and explore letter sounds by using songs. We keep singing one at the moment about the oo sound which repeats "oo oo" which is very fun to say/sing. The story is about the children saving the day which is fab because it's a positive and interesting story.
Sometimes you have to know your child and go at their pace. I'd definitely recommend doing two or even one a day at a time when you're both not stressed (I know easier said than done). I think that this has worked for my DS (who got 6/6 today!) because it stops it being a laborious task - two spellings, lots of praise when he gets them right (genuine praise as I am very proud of him) and then we move on. None of that, there's 4 more still to do, you can leave the table when I say you can rubbish. It also easily moves onto us finding rhyming words and making up rhymes. We also talk about other sounds that have a different spelling or the same spelling but different sounds.
I hope that helps, sorry it's so long I should really go to bed!