I think honors usually ends up being about the top 15% percent of the class. There are a few classes where everyone has done so well they've had to allow more people to honor. IMHO, P/F/H is really nice because you're not scrambling for every point, but you still get rewarded for working hard.
Pass level is absolute and set before the tests - e.g. you have to get 65% of your answers correct (no curve).
Chicago sounds much more consistent..
In Urbana, when I was an M1, the minimum pass level was never set higher than 60% for exams (and never really set lower either). There was no curve, per se, but questions that a very few number of people answered correctly or that were deemed to be "unfair" were thrown out, or additional answer choices would be counted as correct. It always seemed that this happened to a greater degree when the class average was low and a lot of people were below passing.
Anatomy Lab was 65% (13/20) and sometimes a question would be thrown out if a tag was found to be slipped or something, but for the most part it stuck at 65%.
In Peoria, for M2, the pass level works similar to Urbana as far as no curve but post-test "adjustments" to the passing level. However, the minimum pass level was generally set around 70%. This is, definitely, what made M2 harder. I tended to score in the 75-85% range both in M1 and M2. The difference in M2 is that since the MPL is higher, you are cut much less slack. During M1, given the cumulative nature, I recall going into finals week I would have already "passed" most of my lectures even if I had skipped the final exam.
Speaking of which, there's an urban legend at the Urbana campus about the Anatomy Lab. Supposedly a few years back, there was a well-prepared M1 student who had scored enough points (at least 52/60) to where he wouldn't need to take the final Anatomy Lab segment test because the MPL was going to be set to 65% or 52/80. So, he decided to not study for nor take the Anatomy Lab test, was absent for it, and was failed from Anatomy Lab on character by request of the lab professor, Martha. He then refused to sit for the notoriously and ironically impossible 1-day, 80-question, cumulative Anatomy Lab make-up test, and was forced to repeat M1, Anatomy and all.
I don't know if that's true or not... but it's a sad story if it is...