Surely you mean to say "intestate," meaning he died without having written a will? It does not mean "interstate," or out of the state. One can look for the estate records, which may be available under historical records at FamilySearch. Forget the search box and look under "United States," etc. Estate records may be minimal if he did not die with minor dependent children or there were special issues, but it's still worth a search. If not, then check land records, etc.
Records for the Society of Friends are readily available through CD format. Many genealogy libraries will have that available. And those are just the abstracts of bare vital data and membership changes. Microfilm of the original records themselves can be ordered through a local Family Search library location. If a member was dismissed from membership for joining the military, it should have been recorded, if the record survives, and most of them do. The Friends Historical Collection at Guilford College in Greensboro NC covers the NC & SC area, and is an excellent resource for those with Quaker ancestors. Also, the Quaker Roots mailing list on Rootsweb is one of the best mailing lists on RW.
I'm not an expert on military records, but the Revolutionary War did not get intense in the South until the early 1780s. If someone died in 1779, that seems a bit early for military service to cause an issue with his local Quaker meeting in NC. If the military service was in another state, it's possible it's the same man, but one would want to be very cautious about not confusing records for two different men. Signatures or marks on deeds or other records can be compared to help identify a particular man.
Y-DNA testing for an appropriate Benson male would be one way to see if he belonged to a different biological family group. And mutations or changes in markers can differentiate between family branches, if they occurred in that family. If it is done, 37 markers is minimal to draw any conclusions.