Your analysis is about the initial spread, almost irrelevant to bettors by the time they place their bets.
And just BTW, even this one conclusion is incorrect. If it were correct, all the initial lines would be the same. They are not. Some understand that there are teams that bettors are much more likely to bet one, and more the line accordingly.
You are one of the many who don't understand how lines are made. You can find a list of the Vegas Power Rankings on a variety of websites, including ESPN Insider. Do me a favor...get the list, do the math, and tell me how many lines differ in any significant way from the expectations. You won't find any. Once again, the movement of a spread a point or two in one direction due to the pressures or expectations of the betting market does not disprove my point at all. I already said this in my initial post, that lines will be adjusted but only by fractions. You aren't going to find a seven point swing anywhere in there.
I'll simplify my point: let's suppose, theoretically, you have the New York Jets with a Vegas score of 23 and the Buffalo Bills with a Vegas score of 20. The Jets are playing at home, which presumes they should be -6, and there are no notable injuries. However, historically, the Buffalo Bills have beaten the Jets the last 9 times they've played by an average of 15 points each time. On top of that, though, the Jets are an objectively better team. Many would point to the Bills "matching up" well with the Jets, or having personnel that is specifically capable of beating the Jets, though not as good at beating other teams.
What do you think Vegas would do in this case? Do you think they would adjust the line to make the Bills favorites, since the public is going to put 80% of bets on the Bills, confident that their style matches up well with the Jets and that the Bills will win their 10th straight game?
If you think Vegas works like that, you are mistaken. Vegas does not do that, which is what 95% of sports fans do not understand. Vegas might adjust the lines by a point or two in one direction, and they they are holding their ground. When you say that "all the initial lines would be the same", they basically are, though as I've said, there may be a slight swing of a point or two based on the betting trends independent of probability, and actually, that's where good handicappers make their money, by exploiting an overreacting public who bases bets on indicators they think are important but are not. Vegas bookmakers typically view past performances as virtually irrelevant and focus on the overall strength of both teams (Jets 23, Bills 20) in their index scores. Nor would they add points for one team for having "more bulletin board material" or "extra motivation and emotion" nor would they drastically change a line due to "fewer days rest" or a west coast trip. All of these scenarios could slightly change the line but nothing dramatic in any way. That is how Vegas does things, using cold, hard reason based on nearly infinite data...the proof is just looking at any lines during any week and matching them up to their indexes. They always fit within a point or two unless there is some major injury.
