a double layer 1.1 would be stronger than a single layer 1.9 with a pad packet sewn to it. a true double layer has 2 structural layers. it would essentially be 2.2 oz/yd. and should be stronger and more durable than single layer 1.9, or 1.9 with a non structural pad packet sewn on.
yep, it was a single layer.
2 layers would be plenty strong.
one thing that i & others have discovered is that a really small or abrasive hammock support can cut into the hammock.
how much depends partly on the hammock material as well.