[X] Ask how you can make him comfortable here. What sort of fabrics you can have his room furnished with so he can be properly comfortable, what sort of decorations he might like for it - he did mention having his own space being pretty new to him.
[X] Ask about incubi themselves. How are they created? How does ageing work if at all? In all your (ahem) research you never found evidence of one that looked older than twentysomething, so Belial's appearance kind of begs some questions.
[X] Ask how things have been going with the others so far. Since interpersonal relationships with demons are understandably going to get complicated, and you're sure Makram and Issachar will have had Opinions if not Jun-ho and Abzu too.
[X] Ask for more details about the life of an incubus in the infernal plane. Is it hard? Easy? Fun? Work? Do incubi hang out with other incubi after their shift ends? Is there some kind of ultimate goal or 'promotion' to look forward to?
[X] Ask about the implications of succeeding or failing at drawing him into a polyamorous web of relationships. What happens to the contract that sent him here and trapped him in the material plane? Is there a risk of him bamfing away back to hell at some point?
[X] Ask how you can make him comfortable here. What sort of fabrics you can have his room furnished with so he can be properly comfortable, what sort of decorations he might like for it - he did mention having his own space being pretty new to him.