Thanks for your letter
It seems as though things are tough going at home right now. Sounds too as though dad is feeling angry and sad about the split with your mum but taking his emotions out on you.
What he is threatening to do, such as removing your belly bar could amount to physical assault (especially if you resist) and to take you to live with him and your aunty are emotional threats.
But in answer to your question about whether you have the right to say where you want to live, yes you do.
I think it is fair to say though that dad is probably feeling quite alone and sad at the moment if your parents have just split up. Everyone is going to be feeling all sorts of emotions about what has happened, but this will calm down.
Can I suggest that you and your brother are as supportive to dad as mum, although it is sometimes really hard not to take sides when parents split up. Dad will still need your love and support.
Take care
Sam