Thank you for the advice.
The good news is, we broke it free last night! We went and picked up some PB Blaster yesterday afternoon then my husband rigged up a tri-pod/winch system to see if we could loosen the adapter from the well casing housing. After the lubricant sat on the joint for a short while, he put some tension on the winch then started hammering from the underside of the T-puller.
After about 4 good whacks, the adapter began to loosen and then broke free!
We pulled up the unit and were very happy to find that not only was the pipe only about half as long as we guessed, but also found that the water pipe wasn’t galvanized. It was heavy, but nothing we couldn't handle!
I have to say,
I’ve been patting myself on the back since then because all of my hard work and research led me to the exact pitless adapter set-up that we found in the well! As mentioned in my previous comment, the adapter is in fact a Maass Midwest J Style weld-on type. Now comes the job of figuring out what pump we need as a replacement.
I want to mention what we observed on the outside of the pump, which was a thick black film. After doing some additional reading, I ran into some information that could explain the gunk on Wisconsin’s DNR website in which they warned of the potential for drinking water contamination from submersible well pumps. I cannot seem to find good information about this pump as the numbers on it don’t match exactly with any Sta-Rite model. (I attached their document here.