“The definition of mishing (as I understand it) is that you don’t eat stuff that was produced outside of your home/ without your supervision. ”
Again, that is the definition as you understand it. This does not make it so. (plus even lishitascha this isnt accurate because you allow for wine and matzah)
I’m familiar with this idea behind it. But the bottom line is there is no “hilchos mishing” So whether mishing includes eating mass produced foods, foods from your Rebbe, sister, son, married daughter nephew Doesnt depend on what the definition is as you understand it.
Your vertel about mazal fals flat too. I’m not sure how my eating food that you dropped a crumb into r”l is dependent on your mazel. In your last paragraph you acknowledge this that it depends on my bad luck if the worker mixed his bread in.