Like damn NOTHING gets done around here💔💔

Of course the first step to writing anything like this is to do research into what changes this kind of trauma has on a person, (but it seems like you’ve already done that), and I think the problem here might be that you’re overthinking what foreshadowing means. 

Foreshadowing doesn’t need to give so many hints that a reader can put the pieces together -- it just has to give the right pieces so that the final picture isn’t contradicted by anything.

Let him react the way he naturally reacts at this point in his life.

If he falls apart, then let him fall apart, and don’t worry whether the reader looks at that and goes oh no he was probably abused, or simply huh there’s more going on here somewhere. If he’s well adjusted, then the second version is all you need to support the reveal later on.