My parents adopted four children from Ukraine in 5 year time span.
The first two were biological sisters (9 and 10 yrs old). One of them immediately hated us after the adoption was finalized. She is now 23 and has no real connection with any of us besides her biological sister. She has that fantasy mentality that all was perfect in Ukraine. When in reality, it just wasn’t. She always says that she will go back to visit, and we always encouraged to her. She has completely distorted what it truly was like over there, and we hope that if she visits she’ll have a better understanding that we were only trying to help.
My other siblings are completely different. They definitely have certain things engrained in them, but they do have a better understanding of life and work.
You sound like you are doing all you can to give your son a good life. If he does decide to find his bio mom, I’m sure he would still come back to you guys. It’s easy for childhood memories to get distorted, but he’ll come to understand that you guys gave him the life he deserves.