If the BTC was returned to the OP then there is no need to send any KYC therefore what is stopping you from doing that?
When this issue started I was one of the users that advised the OP to never send you any KYC because no matter what was sent you would claim it was doctored or suspicious and would reject it. I reiterate that sentiment, the OP should never send any documents to you.
If you want to send the 35,519+ EUR to the OP bank account you might need KYC but to send the BTC back you do not need any KYC. Just do it and get it over and done with.
Because an Arbiter would have to comply with laws and release information to us unless, a Judge would say the Countrary. Any of the 2 solutions would be suitable.
But don't worry, the OP cannot provide his KYC to anyone because he is not the account owner. I wish to be wrong but, I have to assume we will stay here for another few years.......
Thank you