Umm... the band office and the band health office or nursing station are different things. The band office is like city hall in any other sort of community; they deal with civic administration. The nursing station is the clinic or hospital in the community; they're usually staffed by nurses around the clock and have physicians on site on a rotating basis except for the larger communities where they'd have a more comprehensive health centre. The nursing station is the first contact in the system for Fisrt Nations residents. They act as the primary care practitioner in the community and as a liaison between the community and the acute and tertiary care facilities in the city. As an example, let's say Mary Crowchild lives on a remote First Nations reserve; she isn't feeling well and goes to the nursing station. The nurse takes her history and does some basic examinations. Mary's blood sugar is almost double the desirable so Mary goes back every couple of days to have it monitored until a pattern of hyperglycemia is proven. Mary is then referred by the nurse to a GP in the nearest large town. The GP and staff provide Mary with the initial care for her Type II diabetes and when she returns to the nursing station for followup the nurse there will have her records from the GP's office and knows the treatment plan. S/he provides primary care to Mary and between them they get Mary's blood sugar back to normal. Some time later Mary's urine output drops off and she starts becoming edematous, especially around her ankles. She goes back tothe nursing station where the nurse does some basic tests to discover that Mary's kidneys have become compromised. Mary receives a referral to a nephrologist in the city; the federal government provides transportation to the city and accommodations for Mary and a supporting person so that she can have a renal workup. Mary's kidneys are damaged but not to the point where she needs dialysis. So she returns home with a low protein, low potassium diet with instructions for ongoing followup in the city. So that's how the band health office or nursing station can help your husband find a referral to a specialist while the band office where your mother-in-law works can't.
First Nations health care is not restricted to "First Nations' health facilities". They receive care at whichever health care facility has the services they need and the bill goes to Ottawa. Many of the patients I care for at work are Aboriginal; a lot of them come from the far north. Our hospital has a wonderful Aboriginal Services department; the social workers there work in conjunction with our unit-based social worker to ensure that whatever supports the patient and family need are arranged for and that there is someone who "speaks their language" (even if it's English!) who can help them find their way through the health care maze. We have sweetgrass ceremonies for patients in their rooms (the only hospital system I know of that allows this) and we have a sweat lodge on the grounds. We also will provide for customary or cultural dietary needs.
Now what your husband needs is the initial referral so that he can start making connections and get a diagnosis. Having a name for his problem will help him a lot! It's possible that his autoimmune condition has nothing to do with his heart problem, but without an adequate assessment knowing that isn't possible. And nobody will stop him from looking for a better fit with his GP, so if he has family in a bigger community, maybe he should be paying them a visit. Then while he's there he could just "get sick" and go to a medicentre where they'll say, "Gee, I don't know why you're sick like this, so let's refer you to someone who can figure it out!"