Hi Lucy,
Sorry to hear of the needed change due to health issues.
Staying in the straight "B" class is going to be easiest when traveling solo. But I would not rule out something just a tiny bit bigger to increase your comfort by a lot bigger. B+s do get huge and I don't suggest you go huge. But you can go inches bigger to get that true house feel where everything feels just like the big rigs, only closer together in a smaller package. There are so many tiny B+ brands out there,
THIS ONE a fine example at 21'-2" long and 93" wide, offered with and without a slide out. The company does take in trades like your pickup and 5th wheel combo. They also pick up and deliver.
Just another option for you to ponder.