Sounds good Jay. You've done enough miles on your DR to know what works for you. When I traveled in Latin America I did not camp. Once in a while I missed camping. When stuck somewhere I'd ask in villages for someone who could take me in for the night. My Spanish is fair as I spent 7 years working, traveling, living there. (Guat. El Salvador, Argentina)
Sounds like you can handle the DR well off road, this is a good thing if you plan to get off the Pan Am and see interior regions. You could spend years
doing side trips/exploring.
I'm impressed by your tire reports. The Kendas sound awesome, and YES they are available in Latin America. Cheaper than most others. 8000 miles is excellent! I just put the Kenda on my list! (I've only used the K270)
Sounds like you are right on top of the electrical issues
I'm sure you'll be fine as you're paying attention. I hope you have an electric jacket, you'll need it in the highlands, especially the Alti-plano in Peru' and Bolivia. Gets cold up there. I like it because my main riding jacket can be lighter and vent better and I can go with fewer layers in the cold. My Gerbing packs small. Well worth it but do note the current draw.
I've ridden in rain but never noticed water in the air box. My air box top is cut off, a La Jesse air box mod. I use a Filter Skins cover in very dusty conditions. Keeps filter clean(er).
DR's do pump some oil from the crankcase to the air box, especially on a new motor .... or if you overfill oil level a bit. I drain it off using the drain tube. You may find the lower sealing lip of the air filter soaked with oil at times. This is pretty normal if you are running on the highway at 75 mph all day. Thumpers do pump a bit of oil at higher RPM's.
I've only crossed water to just above the skid plate, not very deep. No water in air box. Use the drain tube and keep water drained out .... and YES ... do keep the drain tube ON and plugged up. Do not leave cap off as it would suck dirt and water in. Only remove Cap to drain.
Also keep in mind you have a crankcase vent hose that enters the air box. (this is where the oil comes from) Make sure that rubber hose stays in place, is not ever kinked and is free flowing. (mine popped once after I was fiddling with the shock ... pain to put back on, hard to get to)
I am not sure, but I think it may have a ONE WAY anti-back flow valve on it to prevent WATER or FUEL going from the air box back into the crankcase. If this hose does not have a one way valve, I would consider putting one in-line to prevent water ever going into crankcase in the event you fall in a river crossing. This has been a disaster for other RTW riders in the past. (see Colebatch's BAM road thread) I plan on doing this to my bike, have not done it yet as its a pain to get to.
Heat/Engine Temps and the DR
If your engine is correct and it seems to be, then just forget the temp. gauge. I would disconnect it, it will only bring worry. You do not want to know and in any case there is NOTHING you can do!
Best I can suggest is run good Synthetic oil and relax. I have ridden through Death Valley a couple times in extreme temps (118F). One ride, after hours riding I stopped and let bike idle. I just wanted to listen to the motor. I removed helmet and ear plugs (don't ride without them) and just listened to the DR motor. At this point it had been running hard for hours at 75 to 80 mph. It honestly never sounded better. Perfect. Very impressive.
Read up on the Suzuki SACS Air/Oil cooling system. Its really quite good, was developed for road racing in the 1990's. Basically, your DR will never over heat, but of course do try to keep moving. You were right to turn it off when stuck in traffic. I do this too .... can't help myself, even though I know the motor never really gets hot enough to do damage.
Synthetic oil makes all the difference with an Air/Oil cooled motor.
I hope you will post your RR link over on the BIG DR650 thread. There are some really good mechanics over there as well as dealers (Jeff at ProCycle) among others. I know they would all love to help you out anyway they can.