I have never understood why Ensure is so much in favor with medical facilities. I think it’s terrible stuff, the regular Ensure doesn’t have enough protein and has far too much sugar which is not good for wound healing. See if they can get you a high protein, low sugar supplement. You are losing so much muscle mass, higher protein intake may help you to maintain.
When my mother was in home hospice and they dropped off the hospital bed with an air mattress, the delivery man said to leave it set at maximum inflation. I tried it out, it was horrendous, like lying on a lumpy rock. We quickly deflated it. I hope you are more comfortable with the softer mattress.