1. Yes, this seems correct to me.
2. No it does not have the same meaning. The change to “j’avais manqué” makes it seem like the lack of money was at a very precise point in time whereas “je manquais” is clear that this is a continuous event in time. Similarly, the change to “n’avions attendu” suggests that this is an event that is no longer in effect whereas “n’attendions plus rien” is not clear on the fact that expectations are back.
3. n/a
4. The verbs in plus-que-parfait are fixed events in time. There is a date in time to when the mother was put in asylum. Similarly, the personal cost of putting the mother in asylum being directly related to the action of putting her in asylum makes it a fixed point in time as well.

Source: Native French speaker.