Unfortunately no, I haven't gotten the 3rd ending. I was thinking that maybe it was only in the Steam release as I was playing the original Darkling Room version so I Installed the Steam version, same result, no 3rd ending. I must have completed the Saxton Map puzzle correctly though since
the Map is no longer in the book and the slips of paper have vanished from the Inventory.
Became so frustrated so I found a YouTube video of the 3rd ending so at least I won't miss it.
EDIT:I got it now, it was there the whole time...I had assumed that to get the 3rd ending I had to
recite the ritual in the good way but to get the 3rd ending I recited the ritual in the bad way that the DarkFall wanted me to say.
All in all, a very well done game, certainly not a short game. The whole thing reminded me of a combination of DarkFall, Barrow Hill and the Lost Crown games.