Good Luck.

I have had 3 of those metal bottle cages break on OZie corrugations. Use plastic nylon ones - they don't break, they will flex and wear but not break.

Small pumps tend to be a lot of work .. better with longer ones. I have 2 Topeak morph pumps - they are good, the smallest I'd take touring. The presta valves are a lot less work pumping up.

If you need more bottles .. I have put 2 either side of the standard down tube one (not the seat post one - the one in front) - my feet clear them and they are lower than the one you have on the top tube. Later if you go for a main frame bag then these two bottle mounting points may come in handy for water.

Sand will ware away at your rims - it gets onto the brake pads and makes a sand paper .. take some spare brake pads and swap them over from time to time. When the old pads come off you can spend some time picking the sand out of them. Disk brakes are much better, as Chris pointed out, you don't ware out rims, disks and pads are much cheaper and easier to replace.

Flats - snakebites means too low a pressure. Tube ripping around the valve = tyre moving on rim = too low a pressure. You need more tyre pressure! There should be a minimum tyre pressure on the tyre side wall .. With luggage on you'd want more than the tyres rated minimum pressure. The Topeak morph pumps have a rough pressure gauge that can help with the pressure management.