Magnetic switches should work fine as long as they can handle the current. I expect you'll be controlling a relay or MOS with more current drive from the switch. Optical or mechanical switches would work as well and mechanical ones may have higher current drive.

You can use the overtravel stop switches so you'd only need one up/down switch. Exactly how this is done would depend on the overtravel stop switch.

Yes you can use a relay to interrupt power but it'd have to be a very high power relay. There are probably better options, simplest I see is a hidden light switch that gets tripped when the travel reaches end point.