What things does he have? That boy's had far too much freedom.
Order of things is kind of messed up from a story POV, and requires some retcons of Laetitia takes Silviatos's lab. Silviatos's lab would be vacant when Isen arrives (and he would've been absent for over a year), it makes some sense that he takes it and kicks Ulrich out.
Laetitia arrives in late fall of 1221. Apollodorus blessed the idea of adding her, and she took part in the Aegis ritual for ME. I see I need to answer your question about a parma text for 1221: it's a L6Q15 Summa.
https://forum.atlas-games.com/t/seasonal-activities-thread/6263/33
Summer of 1222, according to that was Laetitia taking over someone's lab, Fieltarn's or Jormungand's: both are essentially empty +1 sized shells, their previous occupants having acted as if they were being foreclosed upon (taking all the good stuff out, and trashing it otherwise).