That sounds pretty cool actually. I like the idea of being able to go ethereal. I also really like the idea that ancient structures, and random badness, also existing in the ethereal plane.
Yes, adopted from the D20 Ravenloft rules. Though I'm thinking of simplifying them down further in terms of the circumstantial modifiers that apply on fear and horror checks though, because that kind of granularity is proving too much of a burden on play. Checking off against a list of 20 possible modifiers isn't really my style. I prefer to leave the fortune mechanic pretty light, but have lots of crunch in the resolution mechanics - what happens, not whether it happens. So I'm probably going to just give some guidelines for choosing the circumstantial modifier soon.
One thing I've tried to do though is incorporate the D20 Ravenloft rules into the core rules rather than treating them as an add on. So for example, spells that cause Fear don't follow the format of 'Will Save or panic", they just tend to provoke Fear checks. Mummies don't have a 'despair' effect, but provoke Horror checks. Psionic Blast actually provokes a Madness check on failed save as incidental to the rule that all mental ability damage triggers a Madness check (so if you loss 5 wisdom from a wisdom draining attack there is a small chance you'll also go temporarily insane). Things like that.