You asked how to make sure X uses your xorg.conf. My answer means that you should copy it as /etc/X11/xorg.conf
Then, after X has started, this:
grep xorg.conf /var/log/Xorg.0.log
Should say:
(==) Using config file: "/etc/X11/xorg.conf"
Then, after X has started, this:
grep xorg.conf /var/log/Xorg.0.log
Should say:
(==) Using config file: "/etc/X11/xorg.conf"
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