I’d pop him off to his fathers - and I wouldn’t feel any guilt in doing so either.
I think it will give you time to grieve and recover emotionally. It’s not abandonment, it’s respite for yourself in order to be the best mum possible and I think it sounds like you really need it.
Don’t make a big deal of it - keep it all matter of fact. He has two homes and he’s going to stay at his other home whilst you get better.
Ignore his fathers threats. Your ds has a phone so you can keep communication open without his involvement. Perhaps you could arrange to collect him during his school lunch breaks - take him somewhere for lunch. My ds enjoys this.
Been through a rough patch with my ds so I understand how shitty and cruel they can be.
I find it best to ignore the attitude, give him options , and give advice not orders.
So if he doesn’t want to do chores/help out that’s okay, but he then shouldn’t expect money or lifts.
Having problems at school - ok this is a difficult one. School and social work should be doing more to investigate and finding solutions.
“Refuses to eat with me”. What I’d say - Are you eating at the same time as me or are you doing your own thing? No? Ok that’s absolutely fine. Should I cook for you or would you prefer to make your own? Ok great no problem.
The shoes - if my ds asks for expensive trainers/clothing that are more than my budget then he has to contribute towards them. Otherwise I say well you need new school shoes your budget is £60 you find a pair yourself send me the link once you have and I’ll buy them.
Spending - you gave him an allowance to buy things. Whilst you may not like what he’s bought let him crack on with it. If my ds bought a balaclava I’d prob laugh and ask which bank he was planning on robbing.
If my ds bought anything dangerous I’d remove and dispose of it straight away. Ds could argue/complain all he wanted I’d explain once “buy things that are dangerous and I will remove them. Don’t be so silly in the future,” and it would be end of discussion. Regardless if he continued to complain I wouldn’t respond.