How will the stochastic analysis work for the whole hub and not for the fields individually, is there a place we can do the simulation for all?

Yes, you can define a report group for one hub (in pForecast we call this cluster), for part of a hub or the whole filed, or the entire facility and group them just as you prefer. There is no limit to how many reporting schemes you create and unlimited number of tags and there are no limits to how you combine these in your reports.