I agree with your Moral, but the rest of what you've said here doesn't quite hold with history.
1. The majority of the cost (the war in Iraq) was initiated in the first term; a better president with better advisors (IMO, Iraq II was all Cheney and Rumsfeld) would not have gone to war in Iraq with the flimsy justifications presented. Thus, the continuing cost of that war would not have happened during the second term. We may have seen an expanded conflict in Afghanistan, but there was substantial international support for this, which would have spread the costs around. It's a fair cop to place the whole cost of the Iraq war on the election in 2000.
2. The financial crisis was enabled by four primary factors: loosened mortgage rules from before 2000 (e.g., under Clinton), irresponsible tax cuts (reducing real stimulus available to the government), the war in Iraq (reducing real stimulus available to the government), and increased and accelerated deregulation of financial players at a time when it was known that there were some systematically bad players (see Enron and others). Given that all four factors happened in the first Bush term, it's also fair to place at least a large chunk of this on Bush.
I would fault Norvig's evaluation mostly on his view of a non-Bush presidency. It is highly unlikely that Gore would have been revenue neutral. On some aspects, it is almost certain that he would have been revenue neutral (no war in Iraq, but possibly expanded action in Afghanistan). Even so, the cost of 9/11 outside of the Bush context would be impossible to determine. I suspect that the TSA as it exists today would not exist; I fear that it could have been replaced with something more expensive (although hopefully less disdainful of civil liberties and the Americans they supposedly protect).
There are other things about the cost-benefit analysis that don't sit right with me as I'm reading them (the way of thinking of a vote as worth 600,000 vs pennies; it seems that more rational math would still be 600,000 vs 20,000), but it's the weakest part of the article to that point. I know what he was trying to do—but I don't think he made the case that it's patriotic to vote based on a financial analysis. (I think it is patriotic to vote, which is why I do vote.)
Everything before is a good summary and pointers to other people doing solid analysis.
The remainder of the article is fully political and can be treated as such (even though I personally agree with him).