I wouldn't focus on anything Viva related, since it was very independent of the software most people used and still use today.
It's a bit hard to explain, but basically, FP integrated some stuff for an alternative "mode" that would be used on virtual machines, something called Viva Pinball. The FP Exe was updated to include a lot of variables that worked for that mode, which handled some things differently (nudge, high score, credits, etc.). Hence, you will find a lot of Viva variables buried in the executable, but they aren't used for the program itself, nor have nothing to do with the Dev mode.
I never got to use that version since it was only available for a few users who were more close to Viva Pinball, therefore someone more active during that time probably will be able to explain it better, and also answer what is that "Kill Dead Man Timer" variable. In any case, I wouldn't focus much on that.