As implied by my question in the original post about how much a URO seal can be compressed, the seal I purchased is a URO seal. I bought it based on quite a few posts that said the door seals by URO worked relatively well, but that some of their other seals less than satisfactory in some other locations. Until the door closing problem arose, the only problem I had with the URO door seal was the fact that the lower length was about two inches too long, with that two-inch excess occurring between the lower rear corner of the door and the first drain hole. That caused all of the drain hole notches in the seal to be two inches out of alignment and forward of where they are supposed to be. All the drain hole notches were correctly spaced relative to one another, but all were shifted too far from the rear corner. I carefully marked up the seal, cut out two inches of length and butt-glued the ends back together while gluing the lower length to the door and aligning the seal notches with the drain holes. Neither stretch nor compression was required for it to fit.
Before seal installation, I used 3M General Purpose Adhesives and Wax Remover (03618C) to clean the door seal surface and also to clean any mold release agent or finger oils from the EPDM seal.
I followed the seal installation procedures (both are almost identical) by Markbhai and the one provided to me privately by Alfred Esser. I find no fault in either of the procedures recommended to me. Both are precise and extremely easy to understand. The only mistake I think I might have made is in underestimating Alfred's warning to me. He said, "Make sure you really squeeze the seal into the door jamb lip to get a tight fit. It will take perhaps 6 months until the door closes "normal", until then, you really need to slam it: these EPDM seals take a long time to shape themselves. Let me know if something is not clear."
Alfred, you should have repeated that warning about 10 times, because it didn't penetrate my thick skull. I tried my best, but perhaps it wasn't good enough.
I used 3M black weatherstrip adhesive 80019, (recommended by 3M for EPDM seals)
Until it had dried, I had no inkling that there would be any problem with the fit. Everything to me looked like it would all be perfect.
The above comments represent my current knowledge of the problem. Next, I will return to the car and examine every inch of the seal once again while trying to understand if there is something not assembled correctly and where the "resistance" to closure is coming from. It is possible that the problem is an incompatibility between reality (EPDM is stiff and takes a long time to break-in.) and my expectations (no original-equipment-manufacturer engineer or reputable aftermarket parts supplier would design a seal system that takes months or even weeks to start working.)
Based on the last sentence in the previous paragraph, I suspect at this point that I may have done something really stupid resulting in my trying to close the door on a section of the seal that is in a place where no seal is supposed to be. It's really hard to clearly see the seal area between the door and the A-pillar with the hinges and the door detent mechanism obscuring the view.
I will investigate, take pictures and report back.
Thanks much for the interest and comments to date.
Tom Kizer