When I use the calculator I get 24 FL for a 120" 16:9 and for 150" 2.35:1 I get 17 FL. Also, I should note that the shortest possible throw, according to this calculator, for the 150" 2.35" in 16'1". You might want to give yourself a little wiggle room and backup to 16'6" or 17'. It won't change your FL numbers much but it will give you a little bit of room to work. It would be a shame to get it all setup and find out you were off by an inch or so and therefore unable to fill your screen with the 2.35:1 image.
You should check the calculator numbers against the manual and if you can set it up as a table mount temporarily and dial in the throw distances in your room before you invert it and put in on the ceiling permanently.