Short answers, pulled from the story.
Scholars translate the term Theophilus to mean friend of God or beloved by God based on Strong's G2321 lexicon entries from 1958. Bauer lexicon second edition page 358 confirms the meaning includes loving God as well.
The Coptic Church claims this individual was a Jew living in Alexandria during the first century. John Wesley recorded that Theophilus was a person of eminent quality at Alexandria based on the tradition of the ancients regarding his identity.
Alexander Weiß notes in his 2015 study that it remains uncertain whether the term technically addressed a Roman nobleman or served as a general honorific statement. Consequently scholars cannot prove he belonged to the upper class despite the formal address used by the author.
Theologian David Pawson suggests Theophilus could have been Paul's lawyer during his trial period in Rome. Mauck published work in 2001 supporting claims about formal legalese present in the prologue to the Gospel.
Theodore Hase first proposed in 1725 that Most excellent Theophilus referred specifically to the High Priest. Recent scholarship points to Theophilus ben Ananus who served as High Priest from 37 to 41 AD and was the son of Annas and brother-in-law of Caiaphas raised during the Second Temple period.