Okay, so last night I added a spacer on the non-drive side and this seemed to work for me. I was able to get a couple more millimeters of clearance. So, my concern of the non-drive side crank arm not having enough spline to bolt onto the bottom bracket (when utilizing a spacer) is not an issue. Also, when searching for more All-City Macho Man Disc pictures on Google, I found what appears to be a stock build with a spacer.
That said, the stock build is utilizing what I think is an FSA Gossamer MegoExo crankset with a BB-6000 (specific for pinch bolt FSA cranks). For my particular frame build, an FSA Energy MegaExo crankset with a FSA BB-6200 (drive side cup) coupled with a Shimano BB-5700 (non-drive side cup), with a 2mm bottom bracket spacer, works.
All in all, I spent way to much time, and more money than expected, trying to figure out BB and crankset compatibility for this particular frame. Lessons learned: next time I'll stick with buying stock build crankset and bottom bracket components.