#3 is obviously the most important. Being a perennial bachelor, WAF is an abstract concept to me. If the Tokina works for you, then go for it.
A US version of the Nikon 10-24mm is $810 @ Adorama: 2181 Nikon 10mm - 24mm f/3.5/4.5G ED-IF AF-S DX Autofocus Zoom Lens for Digital SLR Cameras, Nikon U.S.A. Warranty That's not chump change, but it's down almost $100 from when it was introduced. Given that nearly every other Nikon lens has gone up in price, I find that noteworthy.
The differences between F/3.5 and F/4.5 is 2/3rd of a stop. I prefer fixed aperture zooms, but I have learned that with wide zooms variable aperture is much less of an issue. In my experience, aperture size is not hugely important at the wide end, particularly in superwide territory. If you want me to elaborate on that, I will in the photography thread.