Braille ninja skills! ????

I do not think lead lines are necessary for any of the examples you shared.

Your attempt at displayed fractions, with a label for the numerators and also a label for the denominators is effective, I think.

Yes, it is ok to use a few different solutions within the same book? Often we need different solutions for different sorts of content, even within one book. (What we should strive for is consistency in transcription of any one sort of content throughout a book.)

–Kyle