Well written and compelling.
As you show, Jerry is a "football" guy, but there's a difference between knowing football and being able to adequately assess talent and how the talent fits in the overall team needs and dynamics. We all have an intrinsic bias, there are coaches that are "defensive" minded and those that are "offensive" minded. Jerry is "star" or "name" biased. It doesn't mean he doesn't want to win, it's just that he will opt to go the big-name free agent route. And, as you point out, that normally means big contracts that become an anchor around the neck of the team.
I would argue that, more than free agency, the salary cap is the primary cause of the Cowboys struggles. There is no doubt in my mind that Jerry would spend into oblivion to win absent the salary cap. Of course, he's not the only one. Little Danny Snyder would do the same.
Jimmy knew the time to leave was when you were on top, not after you fell from the top. He did it everywhere he went. Not many people can and will do that. I don't know what would've happened had Jimmy stayed, maybe we win 3 in a row, maybe not. Jimmy's psychological and authoritarian approach was starting to wear thin. Replacing him with Barry was actually a good move - short term success will almost always result if a relaxed atmosphere follows an authoritarian regime. Same thing occurred with Wade after Parcells. But it's not a recipe for long-term success.
I'm cautiously optimistic about next year and the future. In part because Jerry obviously has stepped back. Had he not, we'd have gone down the Johnny Manziel path which would've been a complete disaster. Just see what happened this year with the Zeke fiasco. I'm cautious, however, because it completely depends on the progression of Dak and whether he can be a capable QB on a Super Bowl caliber team. I don't know the answer to that. He was never supposed to be a rookie starter - he was a 4th round project that was to develop while Romo played the twilight of his career. In reality, Dak wasn't supposed to see the field until his 3rd or 4th year.