Actually my son is almost as big as Superman and he uses a barrier free lift to tranfer it is attached to the cieling.
Regarding pressure sores a custom seating system has kept him sore free also appropriate bed system.
They have beds nowadays that are bladders with fine sand whirlled around by water, like laying on a dry jacuzzi.
Of couarse these thing are way overpriced but I am sure Superman had funds to purchase custom equipment.
His headrest is very similar to my sons.
Our guess is that he may not have had enough hydration leading to an unbalance of electrolytes thus heart failure. My son has to have feeding via a g tube pump 24/7 at a rate of 150ml per hour that works out to be 2 quarts of formula and 1 quart of water in a little over 24hrs.
That is just our guess we know nothing about Mr. Reeves health or care he was given.
I broke L4 and L5 riding a horse still have cronic pain to this day but don't take meds just cope. I was very lucky as my son depends on me as his sole/main careprovider.
Your point about hydration is a very good one... a lot of what I did every day, and knew, has slipped into the dusty corridors of lost memories- back then, it was iced tea and cranberry juice, seemingly by the gallon.
My kind regards to you- having been a sole provider, I know it's a tough row to hoe, sometimes.