Have you killed all processes not needed to run the machine?I also suggest you disconnect it from any network and disable virus protection for a while.If it isn't able to receive data-it shouldn't pick up viruses.You do seem keen to have a new machine,but you are only using this to send Gcode to your machine and not really scratching the surface of the capabilities it has.

I may be wrong about your project,but it must be very detailed to require a tiny stepover of a very small cutter over the entire surface.Could you not use machining boundaries to limit this kind of machining to those areas that absolutely need it?What software is being used to create the Gcode?Just for information my largest ever program had 188 million lines of code and the controller had a single core of less than IGHz speed and 64Mb RAM.