I apologize for the frustration this must be causing and the creative workarounds you've been willing to create for it!
I will try to fix. 
This seems like a good clue: "1) Farr doesn't actually crash at runtime, it crashes when it's hotkey (alt space) is pressed."
FARR has some code that tries to fix up the window position if it is off screen -- something must be going wrong here.

Quick question first, have you tried changing some of the options that tell FARR whether you want it to automatically position itself on the monitor when it shows?

I will be doing a livestream game design update/diary this sunday october 8th, at 12 noon CST, if anyone is interested:
https://www.youtube.com/watch?v=h9-hC6y8Uzk

Screenshot Captor was made for things like this.  You can set a hotkey to do "Grab repeat last size+position" so that your first capture is a selection of the area on the screen, and after that just hit the hotkey to recapture from the same area on screen.  And you just need to tell screenshot captor to save each capture without popping-up the post-capture dialog and it will just stay in the background after each capture and auto save them.