1) 700's or 26's?
With good tires, it hardly makes a difference. There are a few slick 26" tires (ex.: 26x1.2" - 1.4") and these will perform as well as the typical 700c tires. As long as your bike clears 26 x 2" tires, you will be able to cope if you need to buy a tire in a small town.
Apart from issues in the third world, 26" wheels work better on smaller frames (no toe clip overlap), while 700c wheels look better on larger frames.
3) Disc brakes or rim brakes?
Disc brakes are great in the mud or if you commute a lot in drizzle. But rim brakes with Kool Stop pads work well in the rain or snow. And rim brakes have a few advantages:
– all types of racks fit on the bike (instead of only a few models)
– the fork doesn't need to be as rigid, and therefore is more compliant: more comfortable.
4) what about IF Steel Independence? (worth the wait and $$$?)
5) Seven?
Those two are doing racing and performance frames. Their "touring" models don't seem designed for anything but for hopping from one hotel to another. While you might get something different if you give them the specs you want, I think you should order a custom bike from one that specializes in touring bikes, not in go-fast bikes.
Is it worthed? If you are 7' tall or have very unusual proportions, definitely. Otherwise, it's highly subjective. A high-quality bike finely tuned to your body geometry and designed by a great builder will look wonderful and will be a bit better. But it's like comparing a Lexus to a Honda: you have to decide if the added cost will bring you anything significant.
6) LHT? seems like a good knock around frame, but how does it compare?
I think the frame design is very good. However, the most interesting part is the LHT Complete.
7) Those Big Dummies look amazing. is that completely impractical?
If you need it to carry other stuff, maybe. I think it is an interesting option for tours out in the barren land, where you need to bring gear for all sorts of weather, food for 5-10 days, tools for all kinds of emergencies... or if you tour with a weaker partner and carry some of their stuff. But for touring in more "standard" conditions, I prefer a standard touring bike. Now if I had to choose between touring on a Big Dummy and on a go-fast bike with 700x25 tires, I would take the Big Dummy without hesitations.
Bear in mind that I don't have a Big Dummy, but I have a single and tandem bike and have toured on both.