If trip A has a saturday night stay and/or 7 day stay requirement (as seems likely) wouldn't the nested trip be a clear violation of the rules - as SAT lawyer has provided links to?
Isn't THAT another of the typical uses of back-to-back ticketing? (I'm not convinced that just flying all segments puts you in the clear...)
I know nothing about Delta.. and have never flown them... but I thought this was an interesting thread so looked at those links...
It seems a pretty clear statement to this "newbie"!
How about flying the nested portion on a different airline?