I think the distance is good enough, just that you don't wanna put your tank right in front of the water where direct sun light will be on the tank.
if u gonna paint or have a background, then with the curtain down, it should be fine.
I never get shock by my tank.
actually you don't wanna turn everything off every time you have to do something with your tank. it will scare the fishes every time your powerhead turn on and off, and turning your equipment on and off will shorten their life time.
or if u r really scare about getting shock, your LFS
should sell somekind of gloves, or just search online for aquarium gloves ^^.
your equipments should be all water prove and should not shock you.
Thanks to AMD, HN1, Zero, partypalooza, thincat, and thominil who helped me in almost every questions. Thanks everyone!!!!!