The way it sounded like did seem a little overly generous. In any case, I'm glad I didn't waste that last will power.
By the way, no, I have not forgotten about the shaken condition. But I am looking for a thematic moment to make use of it. The moment the prince does anything to directly shake Karl's resolve, he'll be playing the part of a jackrabbit on the run from a pack of wolves.
I suspect the Prince will survive the grenade, I'm just hoping it will put a big dent in him, and possibly shake his control of the others