Any 'non-conductive' coolant will become conductive in less than 5-10 minutes of use inside a watercooling loop. Take your time, be patient, leak test and triple check your build.
You'll be fine.
Your local hardware stores sell clamps exactly like that for less (and without the need for shipping).
Based on this chart, 7/16ID, 5/8OD would be 3/4OD clamp size. These clamps are cheap and decent, but you can also use zip ties or worm drive clamps as well. (again, hardware store suggestion applies for all these as well)