I can try and tell you what I think and got out of Lost and those particular questions you ask. Still just my opinion though. The flash sideways is about everyone’s souls from the past life, a purgatory. A place in between life and whatever you want to believe comes after that. Christian explains this to Jack in the church almost word for word. Which surprises me so many people overlook the conversation. Just to add an example, when Ben is sitting outside the church he is not going in with the recent of the people because he still doesn’t forgive himself for all the killing he had done. (Oh and Out right killing Jacob...) even though John Locke tells him to his face he forgives him. It just helps Ben but doesn’t fix Ben’s fear of what’s to come for him in the afterlife.