I'm not an economist either, and it's an interesting question, but his chart just makes zero sense to me.
I just don't see things that way. International demand for oil is going to more than offset any US decline in consumption, unfortunately for the climate, and will be impacted less by declines in US spending than this model argues.
Definitely free money is going to tighten up. But from my point of view, I think the assumption that our economy needs to keep growing the way it has for so long is flawed anyway. We have major resource issues that require creative flexible rethinking and that are fundamental limitors, like water in Georgia.
Everything is going to change. As big as the problems are, that's just how big the opportunities are.
If you are interested in food for thought, as I am too, here's a nifty website with a lot of astonishing info. I love Hans Rosling's and Amory Lov
http://www.ted.com/speakers/view/id/47in's presentations.
http://www.ted.com/index.php/talks/view/id/92Lovins, "We must win the oil endgame"
Aloha.