According to Gregory of Tours (Histories III.17), Leo died in 526, albeit, seven, not six, months after the episcopal ordination.
Abba Epifanius was almost certainly a presbyter responsible for a basilica, in this case the church of Saint Martin in Tours, rather than a monastic supervisor. For other known abba of the Tours' basilica, see [1902]. More on presbyters described as abba, see Pietri 1983.