Firstly, Congratulations on owning a truly awesome machine!!
I had the same model ebfore having to sell it because of moving to Australia.

I can't answer all of your questions, but can offer suggestions for some.

1. Gel pad.
Gel adds a lot more confort. If you can get hold of a gel pad used by horseriders (it is put under the saddle to make the horse more comfortable) and secure it to your existing seat, that might be an option.
I know a few riders who make use of cycling shorts with padding in them to make longer journeys more comfy on the rear.

3. Crash bars
The best ones I have seen for a Dommie have been custom made. Make friends with someone with a welder!

4. After a long search I ended up opting not to get a larger screen. The only ones I have seen have been custom made (I recall Welcome to M & P listing a screen for the Dommie, but I had to order one and the order time didn't coincide well with my trip plans).

5. Soft Panniers
Softies are my favourite.
I had a couple of racks made up for me (to keep the panniers away from the exhaust and to have something to easily attach them to).
Ortlieb make excellent weather and dustproof panniers that you can fit a bunch of stuff into.
Andystrapz.com also make similar bags.

6. Bike Reliability
I can't offer much advise here because my bike travelled less than yours has. I did look into it though and the one thing that repeatedly came up was warnings against overheating (and resultant valve drop - ooeee!).
If you can ensure that the bike is well serviced before you travel, making sure that you include some preventative servicing/replacement for anything that might be particularly likely to take strain, then you should be good. The Dommie is known for being bulletproof! Love it and it will get you anywhere!

Happy travels!

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