I should advance Callidus, using the same method as Erik over here, meaning 25 XPs per year.
Similarly to Grace, Callidus will get
Artes Liberales 1 (5 xp)
Magic theory 6 (105 xp)
However, much of Callidus' time is spent assisting in the lab, and much more time will be used on Area Lores.
In the end, I think I will not track Callidus' abilities. Though I suspect Callidus' Magic Theory score will mirror Bausas' at all times.