Sorry to hear about you dads poor health Maggie, I will keep your family in my prayers.
Sounds like you are going in the right direction. Fresh juices have the enzymes that help the body heal it's self. Could the ill fitting dentures be the result of weight loss? Gum shrinkage, bone loss?
Goji Berry Juice contains some polysaccharides which control the pituitary glands that produce HGH (human growth hormone) which is a powerful anti-aging hormone.
A nice ripe avocado would be easy to eat and very nutritious. Slippery elm bark was used by Native Americans and various healers, and was at one time listed in the US Pharmpedia. It is very nutritious and was given to "invalids".
It is also very soothing to the mucus membranes, and has been helpful for coughs.
Bed sores can be cause by friction, but are mainly caused from pressure, so another name would be pressure sores or decubitus ulcer.
He may have several things going against him. Weight loss, thin skin, poor nutrition, and age. The area needs to be kept clean and dry.
If I was trying to help someone heal, I would work on increasing the circulation. There are several ways to go about it and I would incorporate all of them. Get the body up and moving every two hours at the least. Massage the area. Hot and cold compresses can be of help for getting the circulation going as well. Herbs that increase circulation are cayenne pepper and ginger. A delicious way to take fresh ginger is to juice about an inch with carrot, beet and apple. Fresh air and deep breathing. Exposing the area to about 15 min a day to sunlight. You also want to be well hydrated.
You may want to purchase some "finger tip" foam for his chair and bed. He needs to change his position every two hours, when in bed or in his chair.
There are a number of products that can be applied directly to the ulcer. You may want to check with his health care professional for that. I did a quick google search and
Terrasil appears to make some promising claims (I mention this one as it contains silver oxide), honey, comfrey mixed with slippery elm are also some things people have applied to the sore.
I am just sharing some hints from my experience with "bed sores" and this should not be interpreted as prescribing medical treatment. Medical treatment should be sought of your health care professional.