Yes I mentioned pulleys but forgot to say you should gear down 2:1.

My machine easily obtains better than 0.1mm, often measure with the caliper and find it's within 0.01-0.02mm and that's on 1:1. Assuming the molds are out of wood you're surely not going to be able to measure much less than 0.1mm difference?

I think using 10mm pitch screws is more versatile since you always have the option for higher feedrates than you could get with 5mm pitch should you need it, at the expense of worse resolution of course.