[X] Ask how things have been going with the others so far. Who does he like the most, who does he like the least? If it's going to be poly, whether or not the others actually like each other is more important than ever.
[X] Ask how you can best make him comfortable. While it's hardly an immediate priority for him like it was for Belial, both due to the lack of hypersensitivity and the fact that his body isn't strictly speaking 'real' anyway, he may at least appreciate the gesture. And hey, you never know.
[X] Ask about the whole 'wishes' situation. How do they actually work? What can or can't he do in pursuit of granting them? How do they meaningfully differ from his own inherent powers he seems quite happy to use at the drop of a hat?
[X] Ask about djinn. How they're created, what the particulars of their longevity are, why they're bound to lamps, what their purpose is. With your chance meeting with the marid in the risen temple, you're especially curious.