Good report Frank.
Sounds like you got a bad fill to me also.
You were there doing Nitrox checkout dives with an instructor if I remember from another post. Were you taking a cave or cavern class at the same time or just doing the nitrox checkout dives?
Reason I ask this is that the instructor should have never taken you into the cave that way as part of another class that had nothing to do with the cave/cavern. He really opened himself up to liability and showed a poor set of standards.
With that said, people enter the front part of the cave at vortex all the time, but not under an instructors direct guidelines/supervision unless they are taking a cave/cavern class. Poor judgement call on his part from a liability point of view.
I know folks go into the front part of that cave all the time. divers of all certifications do it, but to do it with a student as an instructor who is not teaching a cavern/cave class is just asking to get his butt sued off in the event something bad happened.