In the book Forgotten Patriots AA and American Indians in the Revoluitonary War...published by the DAR (new edition came out in 2008)..there are a number of PROCTOR's from Charles Co. MD listed, in the section for Revolutionary War Service Maryland 1775-1783. However there is no Joseph Listed.
(Charles, Francis, Henry, Leonard, Thomas and William.)

The author writes that the publication staff at the DAR will continue to work on this project after the publication of the book..so it is possible that you might be able to get additonal information.
You can write to them at: Forgottenpatriots@dar.org..or from a link at their main webpage.

Selma