can anyone provide/refer a proper OO type helper class for managing a singleton of the SessionFactory and then also for managing Sessions?
You might like to consider making your DAL less concerned with managing NHibernate sessions by leveraging NHibernate.Burrow (or implementing a similar pattern yourself).
"NHibernate.Burrow is a light weight middleware developed to support .Net applications using NHibernate by providing advanced and smart session/transaction management and other facilitates."
If you decide to roll your own there are some useful links at the bottom of this page:
A useful google search term would be 'NHibernate Session Management' and 'Contextual Sessions'...
There's no shortage of ideas - you could say there are too many choices, hopefully opinion will start to gravitate around Burrow or something like it...