I haven't read this whole thread, but I have a little bit of experience with the KTM 990 Adv ABS off road. It's way too difficult to turn off. You start the engine, then old the little button in the middle of the instrument panel in until it blinks, then it should be off. I don't now how to tell for sure that it's off other than trying to lock the rear brake to see what happens. You have a certain number of seconds to push and hold the button after starting or it won't do anything. After having ridden for many months without doing any serious dirt, then finding myself going downhill on a gravel road and unable to stop very well, it took about half a dozen tries before I finally got it to turn off properly because I didn't get the sequence or timing quite right. I corrected that problem the next time I went in the dirt.
When going down a hill with ABS enabled, the rear brake is nearly useless. The front brake is better unless you're going over washboard or loose rocks, then it's not much good either.
If I were designing a bike like that, there would be a switch just like the high beam switch so that you can quickly turn ABS off or on, and there would be a light or something to indicate that it's off. Maybe a real bright yellow one so that you're not accidentally riding with it off when you didn't mean it to be off.
It's not very nice to discover ABS is still on while you're on some steep loose downhill section where you have a good reason to need to slow down.
I happen to think that KTM screwed up in designing the control for turning ABS off.
__Scott R. Nelson, 2008 KTM 990 Adventure, 2001 Honda XR650L, Folsom, CA