Hello, I understand your feeling and I appreciate your concern towards your father. Black stools indicate that tour father is losing blood some parts of his gut so he needs immediate evaluation of his losing blood and also the.site from where he is losing if mot done asap his hemoglobin levels may still go down.and.he.May feek still weak and also he may feel breathless and there will ve too much pressure on his heart to pump blood that which is not good for his health at this age. So kindly take home to the same doctor who told.you that he is losing blood or to the better place where you can get better treatment. Take care of your father Thank you