First, I hope you don't mind a survivor's reply to your questions and issues. Second, I'm very sorry you and your family have to go through this.
You are asking questions surrounding some of the very most fundamental factors of Child Sexual Abuse (CSA). Given this, I urge you to put all reactions and decisions on hold until you recv ample knowledge about it.
Your post is chaulk-full of common issues, all of which can be fully explained and addressed through reading here and in the books in our bookstore (accessable through the front page).
two aspects I would urge you to tread carefully (avoid verbalizing) are these:
I just don't understand how his abuse went undetected and why he went back to many of his abusers.
1) Some of the people who were tasked with detecting his abuse were his abusers.
Please don't blame the little boy for complying with the adults in his life. They began 'normalizing' CSA into his life from the beginning of very formative years.
2) Why he went back:
Again, he was trained, rasied and normalized into this. For someone SO young, it became a lot like learning his first language. He was given and trained into a roll in life. He truly knew nothing else. It WAS and maybe still IS his ROLE in life (in his own mind).
Yes, this is a daunting journey. Yes he went through hell and back a million times. And you; You are being drawn into this world no matter how much you object. We were ALL drawn into it regardless of our objections.
I posted videos on my blog that depict horror and issolation. Watch them if you need a view to this hell. Else, I suggest you get to ordering books tonight.
The support and expert material here at MS is vast. Good reading until books arive.
Some will say 'getting a good therepist is paramount
.' I dissagree. You need to get a good fundamental understanding of CSA before either of you can choose a 'good therepist.' Therepists that are 'lesser' can be devastating to individuals and families. Been there, done that.
Welcome to the site...very very sorry you need to be here.