You should paint the interior/ storage areas white as well. It helps greatly for finding things. Also where it will contact the floor, you want to seal that wood. You will spill stuff, and the plywood will suck up moisture like a sponge, and mold and mildew and smell and get soft and rot. Consider the possibility of squeaks as well.
I used to have that same Saber/ Jig saw. When the blade was locked, it was not even close to parallel with the foot. The few times I attempted to use the straight edge method led to a curse fest as the saw wandered away from the straight edge or binded up against it.