Treat it like any training input rather than a treatment. Most people find the footbed feels normal within a week and stop thinking about it. Anything beyond comfort works on the same timescale training does, which is weeks of consistent use rather than days.
Entirely your call. A thick sock softens the pressure points a little, which some people prefer while getting used to them. Plenty of racers put them straight on over sweaty race socks.
Time, mostly. The sled loads the ball of your foot in a position running never does. The Meta Pad is positioned to let those bones spread rather than stay compressed, which is the opposite of what a stiff race shoe does. If the soreness is sharp or stays in one specific spot after recovery, get it looked at.
No. We are focused on one thing and make one thing that you put them on after. Race shoe choice is its own rabbit hole, and there are people better placed to advise on it.
Yes. That is the point. While racing is real and hard on your feet, they're only a handful of days a year. The block is where foot load accumulates.
Arguably more than later. First-timers usually have the biggest jump in foot load, because station work loads your feet in ways training does not. Building the habit before the volume arrives is easier than after.
