Sorry, but I am going to have to disagree with some of what you said.
I find Gutermanns to be OK for clothing, but not good enough for tents and packs and too heavy for sleeping bags. It is basically a cheaper consumer-grade thread.
I agree about bonded nylon thread: definitely suitable for packs and webbing but too heavy for the rest. I use it on an old black Singer which can handle anything.
I disagree about poly-cotton thread. There is doubtless some poor quality poly-cotton on the market, but there is also good quality professional-grade stuff. I have been using Amann Rasant thread, which is very definitely a professional-grade thread. It shows NO sign of rotting despite having been used in my silnylon tents for many, many years.
I also used Rasant on a PU/nylon tent many years ago, and it has showed no sign of damaging the PU coating there either. OK, I do dry all my tents carefully when I get home. Perhaps that is the more important thing.
As for strength - I have tested the strength of the Rasant against similar-gauge pure polyester thread (eg Amann Serifil) and found there is little difference between them. The Rasant poly-cotton thread does not get as tangled as the polyester Serifil thread though, which is a real advantage.
Using a straight polyester thread such as Serifil does have a problem with stretch, although I have not found that it is very serious on a tent. The Rasant poly-cotton stretches quite well. But the real secret here is that you should not have the tension so tight that the thread puckers the fabric at all. With the right tension I find a straight stitch works very well under normal use, even in storms.
Now, all that is based on my experience with tents, packs sleeping bags and clothing. I have not sewn any hammocks, and we know they experience a lot more tension. It may be that my experience would not translate well to hammocks: that I do not know. Be a bit embarrassing if a hammock fell to pieces half way through the night!