If I were your friend in real life, I’d be understanding if I knew you didn’t ask about your husband’s father - on paper, it’s not a situation I’d want to keep any ties to myself. They likely would be understanding too, if they knew.
I think it is like you said before, it is different when you’re still in the situation rather than outside looking in, so I can also understand why you’re trying to manage these boundaries rather than just go no contact. I’d still say going NC would help you more in the long term.
I do get a sense that the light at the end of this tunnel is getting closer, though.