That's a lot of math with no basis in fact if you don't have the triple crank mounted on the bike with the chainline set and the length of the bottom bracket yielding the chainline known.
Do you have a square taper bottom bracket that you can install on the bike so you can mount the crankset with the two rings you are planning on using so you can check the chainstay clearance (to the smaller chainring) and the chainline? There are often differences between the calculated crank spindle length and the actual need spindle length.
When I'm changing bottom brackets, I find it easier just throw the parts together, and check the clearances. Then, I can decide if I need to increase or decrease the chainstay clearance or the spindle length to alter the chainline (taking note of the length of the test spindle that I installed, as well as whether it's symmetrical), and then calculate the bottom bracket spindle length needed. .