AFAIK there is no way to keep the DK for the after game BF.
For the Raanaar doll, you can skip having it restored if you avoid the main room on the fifth level of the catacombs after you get the 3 symbols the goddess asks for. I think that is explained in the strategy guide (didn't try it myself).
I didn't raise my intelligence stat very much, since I didn't need that much mana, but you shouldn't cause any problems with a modest boost, even mostly using melee attacks. Hammer is quite effective, and should help throughout the game.
Asmodheus likes to make deals that he can technically fulfill, but which are not what the other party wanted, or expected.
The Raanaar ghosts are stuck in the past, having lost the memories for some time before their deaths, and reliving a time before the recent war with the demons (or maybe they just don't want to remember). They have some awareness of their surroundings, but recognize you as Damian (it is not a physical likeness, as you can customize your character appearance a fair bit, and play as a male or female). It is likely they are in a kind of dream state, and encountering a human, they work that into their dream by treating you like Damian, the only other human they have had close contact with. At least some of what they say are repeats of previous conversations with Damian.
Damian is evil, and was consumed with thoughts of revenge. He blamed the Raanaar for not letting him leave Nemisis. He wanted the crystal to try to get back to Rivellon, and didn't care about the consequences.
Since you like BD you would most likely enjoy DD as well. There is a 400MB demo, if you want to try it out. The CD/DVD version is still available on eBay, etc, and there is a digital download version that was updated to support higher resolutions (US$5-6 on Impulse/GOG). There are a couple issues with the download version, though, and a patch should be coming out soon/eventually (some NPCs spin in place, particularly one involved in a cutscene in the church, and a few people have had problems with enemy magic causing crashes or not being able to pick up items or use stairs near one or more locations in the Dark Forest).
