12 year old defiance - help

[Twitatwoo]

So 12 year old keeps ignoring my rule of no Snapchat until 13 and downloading it anyway. Last week he was given the benefit of the doubt then less than a week later he pops back up on my friends.
Since his father gave him a phone, we have no family safety appts so unable to monitor what he goes on.
Monday I blocked his Xbox for a day and he wasn’t allowed to youth club this week. He threatened to leave to live with his father because of this.
Surely it’s my house? Surely my abusive ex husband can’t still have control through our son?
I guess my question is, how can I proceed? I do not want to live in fear that he’s going to threaten to move to his fathers every time we enforce a rule. I am so scared I am going to loose him to a father who he used to be terrified of.

When does he turn 13?

@Wrinklefree June

I think I would let him have the Snapchat , it's how they communicate with their mate

Sorry posted too soon , sounds very difficult .

Hmm pick your battles. Snapchat isn't the worst.
Sit down and chat with him.

If that's your rule then take phone away and delete apps. Or just let him have Snapchat and say you will check now and again.

Thanks all I think I just feel pushed in a corner, his father hadn’t had any contact for 2 years and then last year my 14 DD was doing inappropriate things on Snapchat and other apps so I guess I just feel concerned for what he might do. Following confiscation of her phone last April, she contacted her father after no contact and moved there.
I had never been apart from any of them for long periods before then.
He’s got WhatsApp which he talks it his mates on and says he gets picked of for not having SC which if you knew my child, isn’t very believable. He is the most outgoing, kind, friendly young man with so many different friends.
I think I’ve got to follow through with some form of consequence as he’s ignored the SC rule but I think once that’s over I’m just going to have a long chat with him and let him have it.