1C - I like the sound of "and it would allow you to search the tower completely at your leisure".
2A - Well, why not? I doubt this will be a permanent residence for our circle (I mean, just look at the neighbourhood), but while we are here I really doubt it is in Miosguinn's interest to sabotage the wards on the place while he is inside. And if he really wants to do that he can do it anyway regardless if we ask him for help or not, he does specialise in illusions so it is doubtful we would notice it. We already put our life in his hands many times, and he hasn't failed us yet.
3D > C - If the dwarven quarter is close, maybe it would be a good idea to check it out, but we can't forget what our goal is here in the first place. Getting greedy is a sure way of getting killed, as is unnecessary playing a hero. I really don't want to go anywhere where that thing might be found, and that includes the monster colony and right now the library as well. Maybe if we find something we can use against it we can return to the library more safely.
4A - Keep him, one more fighter between us and whatever is out there waiting for us next. Besides, Amena should decide what to do with him, not us.
5B - Eh, if we play our cards right she would be completely loyal to us anyway, so what would be the point in making them slaves? Plus, I'm not sure what the local laws are regarding slavery, but I'm guessing it's not allowed. So we would have to release them when we hit surface or leave them here.
You pack up your possessions, ensuring that the old map is properly secured in a scroll case you keep for emergencies. If this thing is what you think it is, then it could be your ticket to magical power and glory beyond your wildest dreams but it will not be terribly useful down here.
I definitely like the sound of that.