What questions does the narrator ask the raven in stanzas 15–16, and what do they mean?

In stanzas fifteen and sixteen, the speaker essentially asks the raven two questions. In stanza fifteen, the speaker asks, "Is there—is there balm in Gilead?" By this he means to ask if there will ever be a soothing of and end to his pain, his separation from the aforementioned Lenore. The speaker clearly longs for this Lenore's presence, as he ventures "Lenore?" into a darkened hallway, knowing perfectly well she isn't there (in stanza five).
In stanza sixteen, the speaker further extrapolates on the question he asked in stanza fifteen. Previously he asked if there would be any kind of comfort for his pain, and now he begs the raven to

Tell this soul with sorrow laden if, within the distant Aidenn,It shall clasp a sainted maiden whom the angels name Lenore:Clasp a rare and radiant maiden whom the angels name Lenore!

The speaker asks explicitly if he will ever behold Lenore again, if he will "clasp" that "rare and radiant maiden." In many ways, the raven is a projection of the speaker's sorrow and loneliness—a coping mechanism, if you will. Regardless of whether there is a literal bird in the room, the speaker is brimming with painful feelings and desperate thoughts, and expresses them through this stilted dialogue with the raven.