If you have found someone to block him, ask him to write a debit note stating how much money he borrowed from someone on a certain day of a certain year (both words and figures can be used). Pay back the money on an agreed date and then both parties sign it. According to fingerprints, your parents may know these things better, so you can discuss with them how to write them.
For example, make an appointment with him where to meet, such as McDonald's, where there is a door, and ask your relatives and friends who he has never met to prepare in advance. Then you pretended to be single and went to see him. Let's see what he says first If it's almost ready, stand up and signal all your friends to come over. Let him pay back as much as he has, and make an iou for the rest. Of course you can't hit people. Be reasonable.
When you block him, take a picture of the address book in his mobile phone, and you will know the phone numbers of his parents, boss and so on. He dare not stop you from bringing too many people. You said the police don't care, you can sue. The court sent him a document. I hear it won't cost much. Of course, you can write down the interest you owe for so long, just like the bank. If it's troublesome, then don't.
Ask his parents' home, send more text messages, such as his friends and colleagues, and then ask them where your ex-boyfriend's home is, where his parents are and where he works. The more messages you record, the more you can find him in the future.