Interesting questions, Cat. I'll tackle some, and I'm sure others will put in their two cents.
Outside of recumbents, there's two things that could affect comfort differently for a woman than a man: frame dimensions and saddle. Many of us get the saddle we like (Brooks for me!) and put them on all our bikes. Many women have shorter torsos relative to leg length, so some bicycles for women are made with shorter top tubes for a given seatpost length than the corresponding seatpost-sized bike for men. Terry makes some in racing and touring geometry, and Trek has some women-specific models, but Trek's WSD line doesn't include their touring bike (520). If you're not an extreme case, some of the difference can be made up if your dealer will swap the stem for a shorter one, but this may affect the handling in extreme cases.
If you buy a stock touring specific model, everything is tilted towards reliability with a heavier load, and the bike ends up heavier as a result. The frame and fork on the Surly LHT is perhaps 2 pounds heavier than your carbon frame and fork, but you'll also get attachments for racks; heftier tires that carry more weight at lower pressure, cushion the ride, and wear long (and may resist flats better); wheels with more spokes that can support the load without breaking spokes (you hope!) and won't be unrideable if a spoke does break; and rims to support the tires. If you buy a full custom bike, you can get the latest lightweight components, but most stock touring bikes back down a level or two, and the cheaper components add a pound or two. Note that you often need to allow 2-6 months lead time to buy full custom, and you pay an extra $2,000.
Do you need all that? Maybe not, but be very careful trying to carry 20-30 pounds extra on a lightweight carbon bike. It's not built to carry a load, and you may well induce shimmy or break the bike if you load it up. The alternative is to carry the load on your back, and I, for one, would not even consider carrying a 30-pound backpack on a bike. It would be hot, sweaty, and can injure your back.
How did you buy your current bike? Buying a touring bike can be like that, if you can find a store that has them in your size in stock. Leave them with a credit card or ID, take it out for a spin, see if you like it. Or hop on a trainer and see if it fits you. There are a couple of extra "gotchas" with a touring bike. First, not many stores carry them, and they often sell out early in the season. By the end of May, they're usually gone. Second, especially if you carry substantial weight in a handlebar bag or front panniers, the handling loaded will be different than unloaded handling, so the test rides where you picked out your favorite won't mean anything for loaded riding. (I named my bike Iron Pig because it was made of steel and handled like a pig...)
I won't address the buy and train at home vs. buy on site and ride question; I think there's arguments to be made on either side, but it boils down to your choice.
P.S. Just thought of Bruce Gordon (bgcycles.com). You might see if one of the semi-custom BLTs he has left would fit you. He was featured in the latest Adventure Cycling magazine, and I bet he could sell you a bike now and ship it to your starting point for when you're ready to leave.