1.) No, we have no clue what proprietary shitty SMB code runs in an ASUS router for their "share disk" feature (or whatever it is).
2.) SMB1 is considered a security risk. By forcing Kodi to continue using SMB1 you are still at risk. Disabling NTLMv2 auth over SMB1 (which is what those two lined do) degrades the already crap security level to something worse than plain normal SMB1. At the end of the day you are at no greater risk than you were six months ago. The only change is you (and many other users) are now marginally less ignorant of that risk, even if you don't understand it.
3.) The active SMB conf is documented clearly in the release notes that nobody bothers to read.