My belief is that the name on his birth certificate (or a comparable document) should be listed as his first name with his preferred name being entered as "Gus."
Likewise, his Name at Birth should be the one on this document with the "Current Name" being Jones.
Support with birth documentation at "sources" and enter the interesting narrative surrounding this story in biographical materials.Also any naturalization paperwork could be referenced in "sources."
Note to leaders: please correct me if I'm wrong, we do NOT need inaccurate info floating about.
Signed: "This Little Old Reference Librarian " Dorothy C.