1. The recommended spark plug is either an NGK IFR9H11 or Denso VK27PRZ11, both of which are iridium tip plugs. The backfiring could be a lean condition.
If you look at your plugs when you change them, they should be a nice tan around the tip. Do you still have your PAIR system installed? It may be adding additional oxygen to cause the popping as well.
2. If your bike has been mapped on a dyno, changing the final ratio should have no cause for remapping. You have a PCIII, PCIIIr, or PCIIIUSB?
The older units use a serial cable while the newer unit uses USB.
You might be able to use a serial to USB adapter cable to connect to the laptop.
3. 10W40 full synthetic is fine. I run it currently, although I use Mobil-1 4T 10W40 for bikes. It's around $10/qt. An oil change with filter usually takes around 4 liters.
Where in S. Korea? I pulled into Jinhae naval base a couple of times and visited Busan.