2. 15 minute tread, (with the last 2min hands out of water) No float, self-rescue etc, but vertical tread. (5 points)
Are you describing how you did the skill or was the "no float, self-rescue, etc but vertical tread" the mandated way to do the skill?
While the skill is called a 15-minute tread, according to the instructor manual, the performance criteria is:
Tread water, drown-proof, bob or float using no aids and wearing only a swimsuit for 15 minutes with hands (not arms) out of the water during the last two minutes.
I know some people get hung up on the tread wording, but there are other ways to complete it.
Edit: Since the Instructor Manual is part of the Required Material for the Divemaster Course, the DMC should have full access to the performance requirements for each skill they are supposed to complete.