Welcome to health care Magic!
The salty taste in mouth is a rare taste abnormality. may be your father is quite dehydrate due to the furosemide
There may be altered sense of taste under the effect of many drugs.
I would like you to review him with the list of drugs he had been taking recently and also get his hydration status assessed by a doctor.
Sometimes due to chronic illness there can be rawness of mucosa which can give an altered taste
of salt in mouth.
In any case it should be assessed and managed because it is hampering the nutrition.
I hope the advise would be informative and useful for you.