I would think if he has a blood staph infection, he would be running a fever, and very very sick indeed.
In my opinion, as soon as he has difficulty breathing, or has any change in his status, I would call 911.
And I am sorry but since being duped over and over by various drug dependent people in my close family, I lack a good deal of trust. I sure would be attending those Drs. visits with him, and ask him to sign a release of information so I had access to all his records.
You sound extremely kind and caring. Hopefully he is as ill as he states, but seriously I have a hard time trusting without secure, and positive evidence that what he states is true.
Please remember, if he has MRSA and he is using your knives, and whatever to secrete body fluids, YOU are at risk of deveoping the disease, also.
He also is NOT eligible for Hospice unless he is deemed terminally ill by a physician, and Hospice care is ordered.