Although the city of Comers isn't the most ideal place to perform this divinity absorption ritual, as the fallen god is sealed very close by, and if anything else gets out it could doom everyone at the same time, there's no better place than the Heavenly Palace.
This is Andrew's temple, and everything is under his control, so there's no better place than this. Now, it's true that they could do it in any other Heavenly Palace—there are several, after all—but they still decided to take the risk.
The reason is simple. If Andrew can't endure the process, no matter where he is, it will still be a catastrophe. Now, they decided to follow Fluffy's recommendation.
The ritual will be sexual, just as it was performed the previous time. The only reason Andrew didn't want to do it was that it didn't seem right to him. Although they had done it once, it wasn't a good experience.
