Hey Tom2,
So glad you're healing, but I'm sorry you're not really feeling any better.
Hang in there, and I hope having the splint out makes a world of difference for the better!
If you're looking to increase the caloric value of mashed potatoes...using only heavy cream tastes like an oil slick, but I think half and half tastes really good. Also butter. Or ghee, or REFINED coconut oil (it doesn't taste like coconut, I promise). I'm obviously not a doctor, but assuming you don't have any issues with high blood pressure, your kidneys, etc.--a hefty does of salt in the potatoes might make you feel a little less weak.
Take care, Tom2.