Okay, the second section.
For campaign reasons, I replaced most of the demons in the second section with simian equivalents. The Ogre Mage was a Hadumani, the scorpion-tailed thingy was based off an aye-aye (terrifying long-fingered lemurs), etc.
The attack after the banquet was as written in the adventure, except that my group mopped the floor with the attackers, for some reason, and the attackers barely escaped.
The illithid does give them nightmares that night, but not the pointless ones he offers in the dream. Instead, playing on a theme in the cultist's journals, they each have a dream in which a "Black river comes to flood this dry dry earth, and all will change when the waters come." The dreams were personalized to the PCs and each contained a suggestion that the PCs get out of town and travel as quickly and as far as they can. The illithid figures that these meddlers shouldn't be around when he tries to get some sacrificial action going the next day.
Mayor gives speech. Declares martial law, allowing nobody to leave the city (since the illithid wants as many townspeople as possible).
Earlier, one temple in town was quietly taken over by some evil priests "hired" by the illithid -- he gave them some favor, some knowledge or something, in exchange for their assistance. I gave them the trickery domain to make their actions easier; they were very helpful to the PCs up to this point.
The conquered temple was quietly fitted with a method to bar the doors from the outside, and on the inside was summoned a gate to the Far Realms, a swirling black column made of hundreds of thousands of scorpions crawling over one another. When the PCs enter the temple, there's the aye-aye demon there weaving a spell of invisibility around the column, and in another room, the tricksome priest is writing up handbills accusing the mayor of being behind the recent troubles, offering the temple as a refuge for anyone persecuted by the mayor's monkey-demon allies, and saying that at noon the next day, all citizens of the town should gather at the temple to plan a response to the mayor's reign of terror.
Naturally, at noon the next day, they'll crowd as many people into the temple as possible, bar the doors, and use the barghests' emotion abilities to frighten as many people into the gate as possible.
Finally, the illithid will lead a contingent of charmed city guards against the PCs, wherever they're lairing. He'll do so under the influence of invisibility, if he can (e.g., if the ogre mage is still alive), only appearing to mind blast etc. if he must.
That's how I ran things, roughly; hope something in these two interminable posts is helpful!
Daniel