Sha,
I'm sorry but I don't think the link profile is big enough yet to be drilling down into these kind of areas, he said he is losing a small amount of traffic, not that he had tons and now he receives none.
1. True however the link profile is only small so it'd probably not of been focussed on that much so far.
2. True again but same as 1.
3. This is only a VERY small ranking factor and for you to even suggest this as a reason as to why his traffic has dropped by 90% is quite ludicrous.
4. You've mentioned this already, nice link though
I'm not attacking you or saying that you are wrong, actually, all your points are 100% correct however with such a new site and the amount of traffic being so small and with a such a small link profile, I think the suggestions above are too advanced at the moment and the problem lies elsewhere.
If you look at the crawl date, then the traffic decrease happening around now also makes perfect sense because Google has had time to drop you down the rankings for example.