from the link I gave you, USCIS has, finally, conceded,
”Lawful permanent residents are entitled to evidence of status”
That is all the justification you need. If they say no, then DIY Writ of Mandamus for the ADIT, your I-751, and your N-400 is all you need.
Your N-400 interview was 3 years ago. So you should be litigating.