Adjusting gibs on a small machine like this is best done by feel and by how much the table can be moved front to back on the X-slide. If you loosen the gib screw on the thin end of the gib and jog the table, it can pull the gib in damaging it and causing a lot of hard work to get it out.
Loosen the four keeps, then gently wind the gib in until it is about to contact. Put a 0.0001" dial gauge on the saddle with the stylus on the table. Pull and push the table to see how much deflection there is and adjust the gib until this just reaches zero.
The keeps will need to be either shimmed to increase the gap and stop the pinching or have the Turcite gently scraped to achieve the same. When assembled, it should be nice and smooth to turn the screw by hand with no tight spots. If you have the gibs and keeps too tight, you'll get uneven backlash with the most appearing at the unsupprted end of the screw.
Also, the axis motors are quite small and don't like to be pulling hard on a tight axis just to hold position.
Oh, and while we're on it, make sure you don't overtighten the belt for the axis as it can snap the motor shaft if you go silly tight.