Quote:
He is not on our sons birth certificate and so legally he isnt the dad of my son.
Not correct.
He cannot do anything to get parental responsibility (if he does not already have it) without providing his address.
You have a solicitor. Listen to her. There is nothing to do, and nothing happening because his address is not known. It is very possible that any address you got would be fictional anyway.
Keep records of him harrassing you, keep them accurately and dispassionately. Report any criminal offence to the police, whether they do anything or not.
Injunctions do not stop fists.
Engaging with him, allowing his thoughts to live in your head, is the thing to get rid of if you can.