The men who wrote the Constitution were reasonable men. That doesn't mean the rabble rousers and hotheads and so on who were at the forefront of exaggerating every issue and claiming British tyranny in every policy were.
Truth is life: From that article, "Hazen and his staff were authorized by Congress to recruit in other areas to supplement the ranks." does not suggest that it was (or even expected to be) a particularly Canadian unit.
I'm not entirely sure what you're saying here. The men who wrote the Constitution were the rebels during the Revolution, were they not? The "hotheads and rabble rousers" were generally not the leaders.
But, as I said before, I don't see the non-passage of the Quebec Act being a major POD. The British government will try and do something to mollify Canada as soon as they realize the 13 colonies are in revolt. Their problem is with the 13 colonies, Quebec isn't a threat by itself, but they sure wouldn't want it joining the 13 colonies in rebellion. And, as I mentioned before, they're already bound to do it by treaty with France, and giving France an excuse to attack would be the last thing they'd want to do.