One thing about the issues with devices, if you struggle to take them off him, turn off the wifi etc, you can in the longer term do a ‘quiet quitting’ approach.
what I mean by that is change your broadband provider, get the lowest speed you need…one that won’t be good enough for consistent online gaming. When his phone is getting old, don’t buy him another one, don’t give him money to spend on new Xbox games etc. If he can’t treat you decently, you have no reason to be buying him gadgets or treats, your responsibility is to provide the basics only. Aside from using the home broadband, his phone must be using data or a phone connection, how is that paid for? Don’t fall into the trap of believing he ‘needs’ to have a phone connection at all times, go back a generation, and we survived without phones. He’ll be with adults at school, he’ll be with friends when he’s out, if he walks off after dark to upset you he’s unlikely to answer his phone anyway. Also remember that despite the news scaremongering, that most people in society are decent and if a 13 year old is in any trouble they can always go to a shop or knock on someone’s door and ask for a phone call to be made etc.
i know it will feel difficult to do, but i would also recommend trying to avoid the confrontations. If he is shouting and swearing etc, lock yourself in your bedroom and relax and watch tv, go to a neighbour for a cup of tea…basically anything you can do to ignore him. What you need to do is teach him that he will get your attention when he speaks to you nicely, so when that happens, you need to engage with him and give him your full attention.
One mistake many parents make is to be giving a lot of attention during bad behaviour, then when kids are behaving not engage much due to enjoying the peace and quiet…but what that teaches the child is that if they want your attention…the way to get it is to argue.
He’s also been through a bereavement and may have confused feelings…his arguing with you could actually be his way of trying to test you to see how far he can push you before you leave him (illogical as it sounds, psychologically when there is an ‘attachment’ issue, bad behaviour can sometimes be due to wanting to prove their expectation that you want to leave or don’t love them etc).
What about the other child? You say they are close in age? Setting very clear rewards for behaviour could help. So for example if the other child doesn’t shout at you or does chores, give them pocket money and make clear to the problem child what they need to do in order to get the same…seeing it demonstrated in that way could help.
Also, what is happening at school? You need a shared strategy with his school, as you need to find out if they are disciplining enough, or whether he disrespects his teachers. As he has lost his father, it could be that there is a male member of teaching/support staff that he respects, or a grandfather or uncle…someone who can speak to him about his behaviour specifically towards you. It may be old fashioned, but having a man he respects telling him it’s not right to make a woman feel afraid could be the talking to he needs.
If you can get him into any activities, something like Karate with a male sen-sai (instructor) could be a good move, because respect is very much built into that activity and he will have a male role model he doesn’t want to disappoint.
Unfortunately, I think you have gone wrong somewhere and it’s difficult to put it right, so I do think you need outside help of some kind, start with speaking to the school. You should have had some firm basic ground rules in place such as parental controls on the internet and games controllers confiscated overnight, consequences for swearing etc…because those basics aren’t in place, it makes it hard to push back on it,
As well with punishments, I’d recommend a tiered approach. Don’t think on the fly about consequences, have a behaviour policy, just like a school does. So for example a tier one behaviour is a week without Xbox, a tier 2 behaviour is tier 1 plus phone removed for a week etc…that way even before he does certain things, he will know the consequences and it (to an extent) removes that after-argument effect of why he’s receiving a particular punishment and questioning your decisions. You need to lay down the ground rules and lay down the consequences clearly with him as a standard thing, so you aren’t dealing with doing that when he’s already misbehaving. Print it out and put it on the walls if need be, to get it clearly into his head.
The really big thing is to avoid debate over consequences, say it once and then done. If he follows you and is abusive, tell him the abuse is unacceptable and walk away, lock yourself in your bedroom if you have to. The worst thing you can do is keep the combative conversation going, as that’s what he wants and that’s how he wins.
I’m not sure if social services would help at all, if you really are at your end with this, you have nothing to lose by contacting them if you want him taken into care. But be warned that they may be very reluctant to help because unless the child is in danger from you, they have no reason to spend money on a placement…and will do everything possible to keep him with you. However, if his issues stem from attachment fears, then you taking this action could actually make his behaviour worse.
If he does get physically abusive, do call the police. Unless there is serious physical harm they likely won’t do much, but could assist you by giving him a fright/warning, and knowing that you are willing to call them and it’s not an idle threat could make him rethink his behaviour. Having someone outside the household tell him how wrong it is could help, as often teenagers can’t see it. Putting a camera in the room and playing back his behaviour to him could also shock him as well, he may not realise how scary he is.