With the current cosmology, my guess is that Ravenloft exists in the Astral Sea. The Shadowfell, while bearing some similarities to Ravenloft, isn't an appropriate fit. The Astral Sea would be much better, as you can stick pretty much anything in the Astral Sea (From deific heavens to the Nine Hells). Or maybe Ravenloft is a mix of the two? A chunk of material composed from the stuff of the Shadowfell deposited onto the Astral Sea?
And yeah, some good rules for firearms would be nice. Starting with not making them Exotic Weapon Proficiencies. If they're available in a setting, then they should be Simple, Martial at best. They also need something to make them comparable to bows. Iterative attacks are out, sure, but there'll still be ways of getting more then one attack in a round, which bows can take advantage of, but which firearms can't. Bows can also benefit from a high Strength. So firearms need something to make up for those two deficiencies. Maybe Feats which allow one to do a greater amount of damage with each shot, to represent improved accuracy with the firearm? Another idea would be to make Firearms roll against an opponents Reflex Save, rather than his AC, to represent Firearms being able to punch through armor. Just a couple of thoughts, there, with the caveat that I don't know much about rennaissance firearms (Did they punch through full plate? Who knows. I'm just throwing out ideas on how to balance them with bows).