It is essential that you can reach the EStop at any moment. If the EStop is out of reach then by all means add another. Having one for each axis doesent really make sense as EStop is EStop no matter which one you press it will still stop the process.
Two roller blinds, one mounted at each end of the axis with the ends attached to the table, sounds like an extremely good idea to me. Make sure you fit them the right way up so that stuff falls off the ends and does not get rolled up into the blind though.
My machine here is a 3 axis router. Each axis motor is current limited to 2 Amps and the PSU is rated at 24 Volts, 6 Amps. The driver board gets its 5 Volt from the 24 Volt PSU. This setup wouldn't work for everybody but it is fine for my needs.
Something that is easily overlooked when using the Write Wizard for the first time on a new installation of Mach is to click on one of the direction buttons. If you don't then the only GCode you get on the Mach screen consists of Z moves only, everything else is 0.0000.
I just stuck the box on the back of my router frame where it is out of the way and wired to it. If it didn't work first time I knew I would get it working eventually. But as luck would have it first time and rock'n'Roll.
For your wire - used screened cables for everything except the spindle (this will avoid any possible stray pickup problems at a later stage) and earth them at the controller box end only. For bipolar steppers you only need 4 core, for unipolar you need 5 core, not sure if you will be using encoders. Obviously the cores have to be man enough to handle the motor current. Limit switches only need two core but again make it screened cable.
Hope this helps.
Tweakie.
btw. When it comes to earthing - it pays to have one single earth point and earth everything to this single point within your control box. (do not earth the screen of your LPT connection - this is only earthed at the computer end).