1st and 2nd. Should the trail runner always follow

In a first and second situation, there is a chance that the lead runner could steal 3B. And, he could do this on his own. He could steal the base because of a poorly prepared 3B. He could steal the base because of a one looking pitcher. He could steal the base because the middle infielders simply refuse to hold him close. Whatever the case, should the trail runner be compelled to follow him?

No.

There is simply too much coordination of this process to make this a viable option. The trail runner is worrying about his primary, his secondary, a catcher's snap throw back to the bag. How his he to account for all of these things and also watch the lead runner. He can't.

Furthermore, if the catcher has a sign on that allows him to throw the trail runner out rather than the lead runner on a double steal it would negate the efficacy of the lead runner's extra base.

All things considered, I think when the lead runner steals the base in a situation where the trail runner isn't necessarily expecting it, the trail runner must remain at 1B.

There are exceptions to this rule but expecting a trail runner to do this seems unreasonable to me.