The front distance is set by the physical imitations of the house construction. I'd have to do major excavation to widen it, since the bottom floor goes into the side of the canyon. So, 14' 6" is a given.
The 22' 6" is somewhat arbitrary. I think I need to truncate the space and not use the full 32' length that's available, and I want whatever's left over to be useable.
The 10' 8" height is tricky, because it's not that high down the entire length of the room. It's 8' 6" at the back of the room due to the three-tiered floor. It actually requires a more sophisticated model than just a normal room mode calculator.
At this point I don't have access to anything that will let me model the actual room and, to be honest, I'm not sure I could understand it if I did. The alternative is to pay someone to do it, and the best estimate so far is $2500 and the worst is $6500. That seems like a lot, especially given all the other costs. That would buy a fair amount of room treatments.