Hola Antonio,
I'm a certified "Chain Nut"
and have devoted way too much time and energy in watching chain wear and performance over the last 10 years.
You are asking all the right questions and doing the right things!
The standard BMW chain is a mid to low quality item. Your choice of the DID ZVM X ring, is, IMO, the way to go. I've done 250,000 miles on DID VM X Ring chains. Not one problem.
I usually go around 22 to 25,000 miles (40K kms) on a chain ... have done so on various bikes (Tiger 955i, Vstrom 1000, DR650)
Sprockets are important too. If you can afford them ... probably BMW OEM sprockets are best. But JT and Renthal are good too. JT sprockets are made in Thailand and cheaper than OEM BMW sprockets, last almost as long.
But here is
THE THING:
To extend chain life it is best to change your Front sprocket at around 12K kms. Going to a NEW front sprocket at this point adds about 20% to overall chain life. Also, with a new front sprocket you will feel a MUCH smoother drive line. The front sprockets wear fast and can cause a "rough" feel in drive line once they begin to wear out.
The rear sprocket can usually survive longer (especially if front is changed) ... up to maybe 35 to 40K kms. if not too much mud, rain or off road or very hard riding. Rear sprockets will last well if a TOP quality sprocket is fitted. Cheap sprockets die quickly. Wheelies Kill Chains!
If you start your trip with a NEW chain and NEW sprockets front and rear ... then I see no reason to carry any chain tools at all. That is just my take, others carry all the tools. My experience indicates not every chain tool is required on a relatively short trip. I do carry extra chain (4 links), a spare master rivet link and spare O rings). I've never had a chain problem, never had to use spares. I do not carry a chain cutter or rivet link tool. YMMV. IMHO.
Speaking of Rivet link, I highly recommend over a "clip type" master link. A properly installed rivet link is unlikely to ever fail. Clip links work well if installed perfectly. I prefer Rivet type on any bike over 450cc.
Oiling:
Many Rave about Scott oilers. They are great in Rain but make a mess of the rear wheel and can possibly get lube on rear tire. Keep an eye on this.
My method is more work:
I clean and oil my chain daily when on tour. I also clean up the rear wheel, swing arm, spokes, hubb and have a good look around at everything.
This is good because it gives a chance to inspect that area. (tire, wheel, chain, shock linkage, and more) Some prefer the Scott Oiler. The Scott is best if you are riding in constant RAIN .... like in the UK, where the Scott was developed.
In rain, constant oil is GOOD! But in the dry, a common 90 wt. gear oil works fine for me, makes less mess. But Oilers are good if flow adjusted correctly. It's still important to clean up your chain and wheel from time to time.
Modern chains are STRONG and GOOD. The oil we put on the chain is only for smooth, quiet running and to lubricate the chain roller faces and sprocket teeth a bit. Chain links are all sealed, lubed internally. Some riders NEVER oil their X ring chains and do quite well. I like a bit of lube for smoother, quieter running and never any rust. IMHO, YMMV. I also believe a bit of lube on roller faces means chain takes less of a beating at high speeds. (IMO)
Off road on dirt, gravel, I use NO lube on chain at all. If you have a Scott, turn it OFF when Off Road. Wipe chain clean before doing dirt. Oil, dirt/sand don't mix very well in my experience. Dry is best off road, IMO. YMMV.
WD40
WD40 is a great cleaner ... but it is NOT a lube. (acts more like a solvent)
It does prevent rust and is great for cleaning up OIL Grunge build up from too much Gooey chain lube ... keep WD off your rear tire. WD is also a great water dispersant (WD) NO, WD will not damage O rings. WD is my favorite cleaner but can't take it on the road, not for sale everywhere. I use Kerosene on the road.
Slack
You are correct to adjust chain slack with your bike loaded up. You should be on board too (Get a friend to help). A bit loser is better than too tight.
A bit of chain sag in the middle of chain run when unloaded is normal.
With quality chain and sprockets you never will have to worry about your chain. Enjoy!
Safe Travels ....