As you noted... most of your questions are answered in my (and others) spinnshelter reviews. Something I didn't specifically address is what to do about pooling / streaming water. There are three effective ways to deal with standing water in a tarp.

(1) Avoid standing water ... Site selection makes a big different. In many locations it is possible to find spots that are not prone to standing ground water. Ideally you want a slight slope away from the tarp, vegetation, and porous soil. Ideally with overhanging trees and a good wind break. This does mean that you will want to avoid setting up a tarp in the middle of a high traffic (packed down) campsites than are in the bottom of a bowl. This works well for one or two people... but isn't so reliable with larger groups.

(2) Bathtub floors ... Some tarp users bring a ground cloth which has a fabric lip around the edge like a bathtub floor of a tent. The "floor" is typically smaller than the tarp footprint so outside water and any condensation that accumulates will end up on the ground, outside the floor.

(3) Raise above the water ... use something like a Hennessey hammock or sleep on a thick air matress.