Yes it's the spindle I used on youtube. Chip has one too...

It works well with aluminium as it is much much stronger and has lower run-out than a Kress or any router.

230V is fine - it's generally from China/Hong Kong.

You can get a set of cheap collets from ebay, 1mm to 13mm which will fit pretty much any tool in that range as they squash by 1mm (0.5mm for the small ones). The spindle came with a 1/2" collet. I got a 1/4" collet from Arc Euro to use with 1/4" shank router cutters. Don't get the 1.5kW spindle as that only accepts up to 10mm tools which is very limited since 1/2" router cutters are much stronger.

Yes I don't see why not, though I've not tried it yet. Personally I prefer to switch it on and off myself as I think it's safer. You can control the speed with an analogue input, so I see no reason not to connect that to Mach3 using its PWM feature.

Nothing else except don't get less than the 2.2kW spindle for above reason. You wont be short of power. I've never got close to the full 2.2kW. Also you don't need much cooling for it - a 10L bucket with a pond pump works just fine for me and is obviously cheap. Get the biggest PVC tube you can fit as that will help with the flow rate. I've found the VFD that comes with it to be fine...so far. Just don't connect the input leads to the output and vice versa as that makes them go bang.