Your father's reaction is disturbing; Disturbing in that he is causing you pain and disturbing in that he does not want to see the truth about your brother. He is or wishes to remain in heafty denial. You are pulling him out of that dark and comforting denial, into the light of truth.
He may be thinking "how dare you make me face this ugly shit!" "How dare you disturb our made-up phoney tranquility!" He wants you and everyone else to forget about your brother's past and get-on with the next chapter of life in denial oblivion.
Well fuck him! Fuck them! Fuck anyone who would risk a sacrifice of that boy. Jackson, I know this was a painful step. I know it hurts like hell. You feel like you just started an out-of-control fire and there's no stopping it now. I'm reading some pretty clear second thoughts here. You have no need to second-guess yourself here. There's no time or place on this planet that YOU could be wrong in attempting to save a child from CSA.
Dude...you are an absolute, fkg HERO!!!! There's no Arnold Schwartzenneger character or movie that depicts this much heroism. You just made a HUGE sacrifice for this boy you likely don't even know personally...but you DO know him. You know him when you look in the mirror...you know him when you look at our avatars.
You say that "you are scared you've finally lost your family all together." My immediate reaction was that any family who would ignore a potential and likely danger to a child is not worth getting upset about. I know you would like a happy, functional relationship with your father, but from his reaction to what you are doing here...I gotta think he's just not worth it.
Did you do the right thing Hero? Hell yes! PLEASE dont worry about THAT.
BTW: My inner child says "jackson is totally awsome...thank you."
You deserve an award man, way to go. Way to stand up for yourself and protect someone else. What more can we hope to do as surviors.