my wifes mtb, well a Surly Troll, is a XS, she's about 5' , and 26in wheels have the advantage on small frames for not having toe strike on the front wheel. Even for me at over 5'10", I dont have toe strike on my med. Troll, even with larger tires, and its nice not to have it.
A good friend did the divide ride with rear panniers and 2.5 inch tires. He said they were a good mix for trail and pavement, and helped with a non suspension bike.
Your front fork may be working perfectly well if the bike wasnt used that much.
re your gearing, my Troll has basically teh same gearing, and I find that it works great, and I've considered doing the Divide and wouldnt change a thing gearing wise. 44/32/22 and 11-34
As Cycco mentioned, if you havent mountain biked at all, do make the effort to ride trails, just so you develop the basic skills of being on gravel and whatnot. My friend isnt much of a mountain biker, but he did fine on his divide trip.
as also mentioned, a rear rack and smaller panniers, plus some possible frame bags and a handlebar roll type thing should handle what you'd carry, although you may have to take into account money wise a small/light tent etc for weight and space constraints.
I've toured a lot, but also be aware of the aspect of the divide ride of some areas requiring carryng more water etc, so we get back to volume availability of your packing system.
There's also the whole camping out in the wild thing, not to mention the possible temperatures range and inclement weather--and how basic you can go comfort wise / space / weight thing. I figure this trip can easily be a lot tougher than some of the long trips that I have done in other countries, and being out on your own will mean that you'll want to comfortable with all the various aspects of stuff.
Oh, re reach to bars, I personally wouldnt bring the seat forward, but you can easily look into various alt bars that are swept back and are physically closer to the seat. There are numerous of them on the market, I only have experience riding Jones bars, but they are a neat layout and give a nice laid back riding position that works well (but I havent toured on them yet, and anyway, one bar can be great for one person and not another).
all the best looking at the tons of divide ride vids etc that show what people bring and their description of the ride itself, and get out riding on trails and everything in between as much as possible to be more comfortable in this sort of environment (if you aren't already).