hardware-possibilites that came to my mind:
(Edit: sorry read it now that you have probs with the x-axis)
get leadscrew nuts that can be preloaded
sync the leadscrews with a belt (with the belt-pulleys loose but in place, then calibrate to plate, then with current on motors tighten the belt-pulleys to have an even sync)
Edit: There are lots of CR10 groups in various forums (facebook, thingiverse, google-groups, etc.) I am sure they also have some good ideas...
