The Standard Form 180 is very often a complete waste of time. If you can satisfactorily complete it, you'll be sent a Form 13075, which "requires" more of the same information. If you have the information to complete either or both, you don't need the flimsey, unsigned, unofficial "Certificate of Service" you'll eventually receive.
You might try ordering his deceased file. You'll find complete, practical instructions at message #1656, this forum.