Replace Xquartz by http://www.ssec.wisc.edu/~rayg/pub/xfix.tar.gz
With a Cherry Keyboard (german layout):
xmodmap - << EOF keycode 35 = ssharp question backslash keycode 58 = less greater bar keycode 20 = q Q at keycode 34 = 7 slash braceleft keycode 36 = 8 parenleft bracketleft keycode 33 = 9 parenright bracketright keycode 37 = 0 equal braceright keycode 22 = e E EuroSign keycode 38 = plus asterisk asciitilde EOF