What is the sous vide botulism risk if storing meat post-cooking at home?
I'm not sure about your question 3, but as I thought about 1 and 2, I figured the swings would not be too big if you don't open your fridge for extended periods of time: how much air is really exchanged between the inside and the outside if you open your fridge door for 5 seconds - which already gives you plenty of time to get something out?

I figured the internets would have to know something about this so I set about searching for some graphs. Turns out Berkeley has a class that includes an experiment where students measure the temperature in their fridge over a 24 hr period. Most graphs look somewhat like the one on this page, where indeed the swings in temperature from the hysteresis window are larger than occasional increases because of opening the door.

I found two outliers. The first one is from a fridge catering to a large group of students, and the article suggests someone might have put a warm dish in the fridge. The second one is potentially very interesting - the author says she thinks the big upswing is from a wall defrosting cycle in the attached freezer, but that meal time opening of the fridge door didn't do anything to the temperatures.

So it looks like there are only two potential causes for raising the temperature of your fridge by more than a degree or so:


putting hot or warm food in your fridge;
having your fridge do a wall defrosting cycle for the attached freezer.


Other swings are negligible when compared to the natural operating cycle for your fridge.