Confirmation patrons must at least have been beatified. So, no, you cannot directly choose Bishop Sheen as your confirmation patron. What you
can do is to choose the name of a saint that had meaning to Bishop Sheen out of honor for him. For example, when
the former Chief Rabbi of Rome, Israel Zolli, chose to be baptized, he picked “Eugenio” as his baptismal name. “Eugenio” (in English, “Eugene”) is the name of a number of Christian saints – which qualified it to be used as a baptismal name – but Rabbi Zolli chose the name to honor Pope Pius XII (whose baptismal name was Eugenio) for his work to save Jews during the Holocaust. Given that Pope Pius XII was still alive when Rabbi Zolli chose to honor him in this way, there can be nothing wrong with doing so for someone who is now dead.
In your case, “Fulton” is not a saint’s name (it was Bishop Sheen’s mother’s maiden name) – at least at this point – but this was also not even Bishop Sheen’s baptismal name. Bishop Sheen was baptized “Peter John Sheen.” So, if you want to pick a saint’s name in honor of Bishop Sheen, you could choose either “Peter” or “John,” both of which are the names of a number of saints. If you do so, it would be nice to also pick one saint with the name you choose (e.g., St. Peter the Apostle, St. John the Evangelist) to honor along with Bishop Sheen.