Don't panic about thread placement, that's what moderators are for :d.
the concept sounds interesting, i especially like your ideas for replay, and the frequency thing reminds me of the Dr. who audio wispers of terror abot a sentient soundwave let loose in a recording archive, I also love the ideas for randomness and variables.
Unity should work well, indeed the first version of the experimental fps horror game extant, developed by Richard and sander (the actual webmasters of the site), was run through unity web player.
however, all this being said I firstly am not sure about what you mean reguarding 3D first person and! a menue. Do you mean that the menue would act as essentially a descriptive list of in room objects and exits, and you'd need to move around yourself, using audio navaids such as speaking of coordinates or general room info, footstep echoe and audio from objects.
Terraformers and Shades of doom both use this method, and it works extremely well, indeed the method they use has almost become a standard in the audio fps games we've seen.
Alternatively, when you speak of "a menue" do you literally mean menue style navigation as in an if game, eg, you select the "go" command and then "out of the door"
If this method it chosen, I'm not sure how it would combine with fps, sinse in an first person perspective obviously you are moving around in the full 180 degrees.
Perhaps download and trying some of the games I've mentioned might be a good source of ideas.
As to money, that is a problem, especially for audio games. Realistically, the most wide selling audio game sold about 500 copies, and that was exceptionally well, most will be betwene 150 and 300 copies to vi and blind gamers.
Harsh, but true. Also, there has been a couple of cases of bad preorders in the community where preorders weren't filled and people lost their dosh, so people can be suspicious, indeed I recently received my own preorder money that I'd sent to support access in one game project which sadly didn't get enough interest.
then again, with the kickstart model you aren't actually asking people for! money, but for a promise of money, so people aren't making a risk on the fact that the project might or might not happen, sinse by the time you take their money it's happening, so there may be less reluctance.
Even so, unfortunately it can't be denied that the audio games playing community is very small indeed, and not exactly rolling in cash, and I'd rather see a less ambicious project happen than a more ambicious one not happen at all for lack of funds.
That being said, if a certain amount of stuff can be done in house as it were by volunteers, that might help a lot.
several people for instance (including myself), have voice acted in games for free, and you might want to look into some alternative options for music as well.
either way i do very much hope this project gets going, sinse it sounds like a great idea.
With our dreaming and singing, Ceaseless and sorrowless we! The glory about us clinging Of the glorious futures we see,
Our souls with high music ringing; O men! It must ever be
That we dwell in our dreaming and singing, A little apart from ye. (Arthur O'Shaughnessy 1873.)