I think the problem is one cannot know/separate the person from their illness.

I doubt your father knew your mother was going to or actually was chasing you around the house with a knife? We cannot predict anyone's behavior, especially someone with a mental illness? If your father was not there often, he probably did not know much of her behavior, how "bad" it could get or how it got in relation to his children, you and your sister.

Too, what would you have liked instead? We cannot cart your mother to the "mad house"/hospital, no one can afford that and doing so would have impacted you negatively too, because as a child you would not have understood. It is hard being a child, even an older teen, because our experience of the larger world is so limited. We generally only know our own family well and we have adapted to that family and its situations by default/because we have had to as that is all we've had.

I was thinking about the five year old boy who shot and killed his two year old sister and how, no matter what, both he and his parents are hosed for the rest of their lives? He can't be "taken away" and raised "better" because he'll always know what "he" did and can't possibly learn to believe, like we adults might, that it was not his "fault". He killed someone, his baby sister. Then we have the parents; the father wasn't even there but you know he feels responsible for not making sure the gun was unloaded, was put away? And his mother, it was a trailer, how much smaller/safer can a home be so the children can play and you can hear/know what is going on while doing some other chore that needs doing?

What else could your father have done? Your life went the way it did probably because it pretty much "had" to go that way. If he had burdened you with her illness, what could he have told you? If he had, somehow, put her away, what could he have told you? My mother died when I was 3, my life was forever changed and I spent 30 years in therapy, etc. Our lives can't come out "better" than they do, they come out as they come out. We could not have done something "better" or we would have? If your mother is not chasing you around the house with a knife when the police come, is calm and rational, how can they believe you? It's a he says/she says and the adult almost always has to win that. Nowadays, if a child is abused, they take the child away anyhow, that's the "joke" on kids that are angry at their parents and call to report they're being abused to get their parents in trouble. If the adults are taken away, the children have to be also because there's no one left to care for them?