Howdy Gary,
As to whether it looks like Terry, of that I'm sure you are a better authority than I, it is supposed to be him. Here is his character sketch from the "David Megarry, David Megarry" cast of characters:
Futures Bright,
Paul
Howdy Gary,
The guy talking to Gary is Theron Kuntz, dressed in a Robinhood outfit.
Having the issues right here in front of me I can say that it does indeed represent all of the company employees in 1976. They were all depicted as characteres in the soap-opera strip called "David Megarry...
Howdy Gary,
You mean this one Gary? :p These images come from The Strategic Preview: T.S.R. Jobbies, Nos. 3 and 5:
The Commander in Grief himself:
The whole TSR crew circa 1976:
Dave also created Shlump Da Orc, his alter ego editor of The Stretegic Preview:
Dave loved to draw...