I doubt it makes much of a difference, but MedFaX's upload has outdated executables. I took the executables from the latest version of ACR available in CSR, ran them through Steamless, and packed them with the Theta crack.

Instructions:
1.) Extract Theta Crack and Executables to [...\steamapps\common\Assassin's Creed Revelations] in whatever directory you extracted the game to. Say yes to overwrite.
2.) Delete systemdetection.dll in the same folder prevent screen flickering.
3.) Extract contents of DLC Unlocker to [...\AppData\Roaming\Theta\Orbit\40]. Type %appdata% in File Explorer to reach Appdata\Roaming. (May need to run game once to create Theta folder.)
4.) Run game using AssassinsCreedRevelations.exe. It's just a launcher for ACRSP.exe, but using it prevents a freeze on quit bug.
5.) If you see "Lost Archive" in the game's main menu, the DLC has been unlocked successfully.