'Ariya' and its application in the suttas

To address your first question I would like to firstly point to this topic:

It is also worth checking the Upanisa sutta (SN12.23) in which one finds the crucial linkage between faith/confidence and suffering/stress in the transcendental dependent origination of the way to Enlightenment.

The other questions I would leave unanswered here but repeat my recommendation a separate topic is created to address / explore them.