the messages were abusing me as in telling me what a terrible person I am and how I’ve done so much damage to the family. Lots of ranting about things I’ve apparently done wrong all my life. Mostly about family loyalty. And about never fucking having any relationship with the family from now on and not being welcome to go to my (abusive) brothers funeral?!
Namechangeth - right now, whatever your brother says is impotent ranting because he is ashamed. Possibly social shame rather than parental shame, which is ... well need I go on? - but he has also lost control by you consulting a higher authority, & that's what he's punishing you for.
I know how shaky you must feel (& believe, me, I know what it feels like when a close family member goes super-unreasonable & threatening on you) - but when you have time, please google DARVO to fully understand what your brother is doing right now.
Your head is screwed on - all the things I immediately wanted to write about your first loyalty being to your little nephew, you have already written. You have done the right thing.
For right now, work on replacing your feelings about "my brother" & his disappointing & frankly shocking responses to you with "this man who is failing to protect his child" - a bit of conscious barrier-building for you to help protect your own mental wellbeing.
I sincerely hope that you might be able to have the boy live with you as you wish. If so, your DB is likely to eventually concede that you are comporting yourself as a proper family member & stepping up for his child. If DB does not - you are better off not being welcome to his funeral [eye roll]
Exclusion from family - if they are anything like DB - will not be too much of a hardship for you. It's odd that DB is speaking for other family members as if he's some kind of Mafia boss & they all need to step into line behind him in accusing you of wrongdoing. But chalk that up to testosterone & distress for the short term. Meanwhile - BROTHER OR NOT - please log every threat, every curse word, every name calling.