I have conflicts, so I type:
git mergetool
I then get a message saying:
Hit return to start merge resolution tool
>
I haven't used git for this purpose on Windows in a while, but your config file shows some interesting differences re: program strings.
[core]
editor = \"C:/Program Files (x86)/GitExtensions/GitExtensions.exe\" fileeditor autocrlf = true
vs
[difftool "kdiff3"]
path = c:/Program Files (x86)/KDiff3/kdiff3.exe
I suspect that there might be some issue with the spaces in the program name. Try setting your diff/mergetool executable paths to:
path = \"c:/Program Files (x86)/KDiff3/kdiff3.exe\"