Thanks again for all the new replies.
Negative pop is probably not an issue since I am taking sooooo long trying to get the damn things in total focus. But making sure said negative is clamped tightly in the holder makes sense - I will add that to my next experiment.
Lenses and condensers and everything else I can find have been cleaned till they cry "Uncle!" After my initial tests with the new used Rodenstock, I believe the lenses are indeed the culprits. Word of advice: if your lens only has four aperture blades, you are probably not getting the finest German glass.
Although now that I read Blansky's post, maybe this crappy focus thing is serendipity helping me to find my photographic voice as it were. I can see it now: fame, fortune and millions of my fuzzy photos hanging in optometrists offices all over the world. That'll be an amazing fifteen minutes! Then I can sell my wonderful fuzzy-focus enlarger lens to a Noblebeast wannabe for thousands of dollars on Ebay. Maybe I better hang on to this thing...