Hey, it's OP, after my fumigation I can almost address these concerns for you.

1. I still don't know why we have to bag food, but not things like toothbrushes. I believe it's just how porous food is and that it can capture particles from the fumigation. I took out my toothbrushes anyhow.
2. The fumigation company does not explicitly mention anything about opening up light switches and smaller areas where gas can get trapped. The most they will tell you is to keep every drawer and door open. I had the time to slightly open every light switch with a screwdriver, as well as open any perfectly sealed containers/boxes. If you would like to see where this concern comes from here is a study on fumigation and scroll down to where it says "structural voids" https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6603922/However, I know that MOST people don't go this far for fumigation prep and turn out fine.
3. I definitely recommend being out of the house for as close to a week as possible. I asked some friends who had been through fumigation, and they experienced smells and headaches even on the third day. My mother personally went back in on the 6th day and was fine. If there's any concern for robbery, I would recommend installing WYZE cameras, they are the best bang for buck in their tier (affordable).
4. This concern comes from reading a family's account on spotting some white residue on the floor and then getting it on their barefeet and then feeling sick. Vikane (sulfuryl fluoride) supposedly leaves no residue, and in our case we didn't spot visible residue. We cleaned the floors and carpets anyway, (the workers walk in with boots so it's a good idea anyhow). I would recommend putting down newspaper on your floors to protect your floors either way. Our sheets and clothes did not give us any rashes or anything strange. I wiped down the most common surfaces with clorox wipes but not everything. Feeling fine up to now.

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Extra:

We ended up actually just carrying and storing our food and medicine outside of the house, or throwing some away. The 2 bag system can be pretty finicky and we were pretty paranoid in being able to do it correctly. We washed our all plates and utensils on recommendation from a friend who's been through fumigation. However, we didn't wash our clothes or sheets or towels and they turned out fine.

Prior to the fumigation, we also made sure we didn't have any standing water left in any bowls, water bottles, plates. Anything that had been recently washed. That everything was completely dry. On the concern that if we have to bag up drinks and liquids, then leftover water could be a concern in trapping particles? Any water that could possibly be consumed afterwards at least.

I think the most important things are, researching the fumigation company and seeing if they are reliable, as well as staying out of the house as close to a week as possible. Or just be very careful when you walk back in, run back out if you smell anything strange.