I must have missed something. Where, exactly, are you headed?
I don't think you will get 8000 miles out of a knobby front tire.
It seems a bit too much to change the oil every 1000 miles. I am sure you can get 2000 even 3000 out of good quality oil.
I think changing oil often is cheap insurance.
In addition to your regularly scheduled parts depots, stock a couple of spares with a trustworthy friend at home. Have them ship spares just before needed should you run short of schedule.
I would not schedule front pads, they are small enough to carry a spare pair. Leave a couple extra pair with your trustworthy friend, and should you need to replace a set, have them ship a spare pair to your next depot.
I would replace light bulbs before heading off on the more remote parts of the ride.
Tire pressures about 16/20 pounds on dirt, 24/28 pounds on pavement. Sounds a bit high, but you said you'd be carrying a load.
Extra cables: Go ahead and run spares next to the cables on the bike, zipties to hold them in place, heat shrink tubing to seal the ends from dirt and water. That way if a cable breaks it will not be necessary to remove the seat and tank to affect repair.
A few interesting spares that could save you from a long walk could be:
Set of levers, set of foot pegs, set of gear and break foot levers, a small roll of fuel line, spark plugs.
If I were doing that trip i would definately run synthetic oil and change around 2,000 mile intervals depending on how it is looking. synthetics don't break down with heat and should have no problems with that change interval
you have probably have already been there but the horizionsunlimited web site has tons of travel stories and lots of great info on what you made need. good luck
This is a little off topic from what you asked for, but I've done similar voyaging, and thought I would share my experience.
Being an engineer, I would go over the bike in detail and make a list of what failures could occur on your trip. Assign a consequence of the failure (1-10), and a probability of occurrence (0-1). Multiply the consequence by the probability and develop response plans for the failure modes with the highest product first. A compete engine failure has a pretty high consequence, but a fairly low probability. It might warrant a spare motor at home that could be sent to where you are. Where you draw the line is dependent on your funding, your comfort level with risk, and how acceptable failure to complete the trip is to you.
The only thing I came up that others haven't mentioned is a collection of jets and a float valve. I would also slime my tires.