1. ERC in Section 5 - Enlisted Reserve Corps
2. Abbreviations in Section 6 = Headquarters Detachment, Service Command Unit #1111, Army Service Force Training Center
seeing that he was a cook, my best guess is he was stationed at a Training Center. The TC could also mean Transportation Corps, which was under the Army Service Force.
3. "Course C" in Section 31 = probably a specific or limited firing range training course.
You can read about the organization & role of the Army Service Force during WWII here: The Organization and Role of The Army Service Forces
This is the patch for the 1st Service Command, whose area was most of New England
The patch TopSgt posted is the Army Service Command Patch, each of the 9 Service Commands had their own distictive patches