I've got a Cirkut Outfit camera, with a Century camera model 46 in front and a Cirkut mechanism (marked inside with #612) in the rear. The lens is a convertible type, marked, in the front cell, Gundlach 7 1/2 in. Anastigmat Ser. II f/6.6; the rear cell is marked only 11". The shutter is a Betax #2. On it, I find different f/ settings for 3 focal lenghts: 14", 11", 7 1/2".
The outfit came with a complete series of gears (25 in total, with number of teeths all different) and 2 "fans".
The outfit seems perfectly working, but I need help to solve some questions.
For example:
1) with both lens cells (front 7 1/2", rear 11"), an object at infinity focuses on the ground glass at a distance of 7.9 inches from the center of the shutter: is it consistent ?
2) vith only the front cell ( marked 7 1/2") the same object focuses at about 14" : again, is it consistent ?
3) if I put the rear cell alone (11") in front of the shutter, the focus is at a little less than 14";
4) and, finally, if I swap the cells (11" in front of the shutter, 7 1/2" behind) the focus is at about 6.3" (distance ground glass -> center of the shutter) .

Surely I'm thickhead, but I'm in a great mess. How should I sort the two cells to have the 3 focal lenghts marked on the shutter ?

Second group of questions.
Is there any formula (in case, available on the web) to determine "ex ante" the type of gear (i.e., the number of theets) to be used, according to the focal lenght, the distance from the the subject and the exposure speed ?
OK, a lot of questions. But, this forum is "source of knowledge" most complete ...

Thanks a lot in advance.