Few points:

According to the protocol of how to give rtx, the second infusion is given in much faster rate. If the first one takes about 7 hours for me, the second is around 5-6 hours. So maybe indeed a slower rate at both infusions might be without events for Yosef.

Flares do not allways show up in the bloods or urine tests. Only in 2 of my flares my blood tests showed it. In others and also while smoldering, my labs were not too bad, except from Pr3 which get elavated before a flare. But some weggies are anca negative so this might not give an indication. My wg dr. says to look at the symptoms first of all. We need to listen to the body and be on guard.

Yosef is so young, so on the one hand it is good for him that he is not taking the WG too seriously. On the other hand, too much denial can cause him not to pay enough attention in the right time to changes in his body, and to neglect serious treatment. Maybe some counseling can help him to find the right balance ?

Praying for wisdom and strength.