My major concern was if the test cup I ordered was exactly the DOT test which I guess isn't (but it is close).
Why is this such a major concern? You already acknowledge that your cup test and the DOT initial screen utilize a 50 ng limit. A 50 ng test is a 50 ng test regardless of type.

Edit: The cup test that youre referring to is far from the Immunoassay used on the initial DOT screen. All DOT-regulated tests are 5 panel, not 7 panel.
http://www.dot.gov/odapc/NEW_DOCS/subpart_b/40_13.pdf
http://www.dot.gov/odapc/NEW_DOCS/subpart_f/40_85.pdf


With that being pointed out, about the only thing the two tests share is the 50 ng limit.