I would consider what you are likely to actually call the boy, if for example you decide to use Zeke as a nickname for Hezekiah I'd avoid Zane. If you are just going use Kiah as a nickname then stay away from Kane. If you are just going to call him by the middle name than go with what you would use as a first name if Hezekiah wasn't in the picture.
Personally I like Zane if you are going to call him by his middle name, but Fox if you are just using it as a middle and will call him Zeke or Kiah or Ezzy. (or even if you are going to manage to call him Hezekiah all the time)
I don't think Mccain or Tim Kaine will necessarily make the name Kane more popular, but I do think that Kane/Cain/Kean is just becoming a more used name and if you really want to have unusual names it might be too popular for that, plus there are several variant spellings.