1 - I was tempted to say it's not really a bug, it's super minor and you are the only one using this at least from what's reported on the forum, but the fix is trivial, just reset exit_options when opening the game options, so I did it.
2 - gui options / return mandatory
C - yeah if it can't find the key you just pressed in the following games in the list, then is starts to look for it anywhere in the game title, that's for when you don't remember the whole title ! This thing is made to be used very fast, and I can confirm it does its job well !
D - not sure, well just press return in this case, I won't bother to look why it didn't select it as it should have done in this particular case.