Difficult to know which 'threadette' to reply to....
1 - I rode 28000km mostly off-road on a Hope Pro2 36H rear disc hub (on a Surly Big Dummy) using Avid BB7 brakes and it did fine. (Velocity Cliffhanger rim, DT Comp spokes). The Hope Pro3 hubs have higher spec bearings so should be just fine. The current generation Pro2 (called Evo) have the same bearings as the Pro3.
Hope produce very nice stuff, and I'll continue to use it - only downside is that the freehub tends to be pretty noisy.
2 - You could go 170mm rear hub if you wanted (the latest fat-bike symmetrical, as opposed to off-set) standard). Hope do a rather nice 170mm rear (disc) hub.... (the Hope Pro2 Evo Fatsno). They also produce a 135mm front hub (Hope Pro2 Evo Fatsno 135mm front) that I've got on my newest bike - again disc, but with the additional width, still a reasonably strong build ;-)
3 - Wiggle and Chainreactioncycles.com are good places to buy stuff. Recommended.