Coupla things:
I would have to assume that the "rigger's belt" was originally intended as a POSITIONING device, in other words to keep you from going over the edge or our the door in the first place, not to arrest a fall or even hang in.

Industrial full-body harnesses or rear-connected waist harnesses tend to render you helpless when hanging free.

Hanging from a waist-belt only will eventually suffocate you from the pressure on your rib cage.

Fifteen feet or so of 1" tubular climbing webbing will make a safe and very servicable "swiss seat" harness. I came up with a variation with pre-tied leg loops that was even more comfortable.

A single largish pear-shaped carabiner is a suitable descending device.

Never do anything that involves hanging from a rope without a pair of prussik loops. What goes down may need to go up again.

Resist the temptation to use a knife anywhere near a rope under tension. Many rappeling accidents happen when someone tries to free a jammed descender with a knife. Likewise, keep loose clothing, gear and fingers out of the descender. Use your prussiks to unload the descender if you need to clear a jam.

Put a big knot in the end of the rope, or tie into it. I once rappeled off the end of a rope that I "knew" reached the ground.