sounds like the heart, he needs to get some tests done for his heart..
It sounds like the flu, I had it 2 weeks ago and was very sick, same , symptoms as your Dad...Theres not much one can do but see it through, mine lasted 6 days till I felt better, the chills and sweats were the worst ,Its a virus if its flu so no anti biotics will help, keep him rehydrated with drinks..good luck let us know how he is doing.PS maybe a trip to see the Doctor wont hurt because of any pnuemonia concern..