The Lynx used with the Ridge Runner is just about foolproof. With a GE hammock, I find it is easier to use a partial length - though at my size, "partial" - as in ¾ - is almost "full"). Except in winter temps, I find it easier to position the partial UQ and have it snug. With full size, I have to be sure my diagonal lie doesn't cause a gap. I do use a UQP so it is not as critical.

If you cannot find a friend to help (lay in the hammock so you can inspect the UQ fit), perhaps you can put your loaded backpack in the hammock and see how the UQ is fitting.

And at this point it depends on the UQ - some have a single bungee and can be helped by something like an S-biner on the ridge line holding (pulling up) the quilt bungees. Some, like those from HG, have secondary suspension that provides that extra directional pull. Some have a differential cut so when pressed tight to the hammock, they don't compress. But it's important to identify the top and bottom so you don't attach it upside down. If it doesn't have a differential cut, you need to be sure it is not so snug that it compresses the loft. Note with HG you also have a foot end and head end so those have to be correct.

I am not suggesting that you got it "all wrong" - it's just that there are many ways for it not to work and without someway of seeing how it was set up, one can only go down the list of things that could be wrong.

A 20 degree UQ in 30 degree weather is sort of at the edge for some (those of us who like a 10 degree buffer vs temp rating). But I'd imagine you'd be plenty warm and comfortable at 40 degrees.

HG has that differential cut so you can snug it right up. At full length, you want your end gather loose and your main suspension so it starts to lift the hammock when you are not in it. Again - details we don't know, like the size of the S-biner. But if things are so tight they break and S-biner there seems to be something awfully "off" about your setup.