Hello and welcome to Gente di Mare
There are many De Angelis living in Ascoli according to the Italian Phone Book.
Here is what I would try to do...Email the commune and ask for the
birth act for Pietro. According to the manifest, he was born about 1885.
Include in the email that his father was Beneditto
protocollo @ comune.ascolipiceno.it (no spaces)
If you get a reply, the record should have the address of his birth.
It might be possible to find one of the De Angelis in the phone book with
a similar address.
You could research your family at a Family History Center near you.
They have records up to 1865, so not much help for finding Pietro, but you might find the birth act for Beneditto.
If nothing else, once you get to Ascoli, go the the municipal office and present your information to them. Also, talk to as many people that you meet and ask questions. You will find they are happy to help.