I'm sorry, but I don't understand what you are trying to do with the mini-keypad, but perhaps I can help a little until John is available.
1. Yes, the MSFS SDK defines Bvars as input events.
2. looked at your myevents.txt file a bit and would like to mention a few things I don't understand. Just for example, consider the entry:
C510_ATC_2#(>(A:TAILWHEEL LOCK ON, Bool) 1 == if { (>K:ATC_MENU_2) 0 (K:TAILWHEELOCK) }
i. Why is there a > in front of the Avar (A:TAILWHEEL LOCK ON, Bool)? You would put a > in front of the A: itself if trying to write a value to an Avar, but the SDK would have to say it was a writeable Avar (although some Avars are writeable, most are not). In this case it does not seem you are even trying to write to the Avar at all.
ii. It looks like you are trying to put a value of 0 into a K event called (K:TAILWHEELOCK). If so, you would need a >in front of the K: (in fact K events routinely have a > in front of the K:). But in this case I cannot find a K event called TAILWHEELOCK in the SDK. Where did you find that K event? I did find a K event called TOGGLE_TAILWHEEL_LOCK.
If I'm off base here, sorry and please ignore!
Al