I didn't read the last 5 pages but I have to ask, is yours a flat roof or sloped roof? If a sloped roof, do you know the slope angle (inches per foot)?
https://www.nachi.org/roof-slope-pitch.htm
I have both flat and sloped roofs. For flat, EPDM rubber is the way to go but another good option is modified bitumen which is also known as torch down. I stay away from tar but old roofers know that well. It just doesn't live as long as EPDM and torch down. For a sloped roof, I'd stay with shingles or metal.