Can you give me a link or something about his adoption by his stepfather? I have not heard this anywhere but the threads here, and have never found an actual source for this claim. But a parent cannot renounce US citizenship for a child under 18.
You are hung up on adoption. Whether he was adopted or not is irrelevant, as you note in your last sentence. The question is (a) whether he was born in the US, and (b) whether his use of an Indonesian passport to go to Pakistan proves that he was once an Indonesian citizen and precludes him.