Side sleeper with bad back here, too. I feel your pain. After suffering with a couple 2"-2.5" pads, I tested several 3.5"-4" pads with the idea that the extra thickness would allow more inflation adjustment. Two major conclusions:
1) Extra thickness was critical for inflation adjustment. I get best results around 80% inflation--enough for flexibility and also keeps my shoulders and hips from touching the ground.
2) The Nemo Tensor with its side-to-side baffles did me WRONG. Whether on my side or back, I could feel it making things VERY bad. Length-wise baffles worked much better for me.
A small pad, empty backpack, pile of clothes, or inflatable pillow about under my knees sometimes helps things, too. I haven't needed it lately, but it's an option.
I started with a Big Agness Insulated Q-Cor which lasted a couple years until it leaked (common with BA pads, I later learned). I now use an Exped Downmat Ultra 7R. Only 2 pounds (25"x72"), R7 insulation, no noises....I love it.
Good luck with your search.