Thank you for sharing your questions and ideas. These small cards sure have *multiple* components, don't they? They won't be small in braille.
I think you're quite right to present the bottom area with circles as a graphic.
I cannot think of any useful way to retain the colors that print is using. I would argue that color is most likely a visual repetition of information that is already given by the content of the cards (i.e., which numbers are repeated within a given card and which number is the answer (product or quotient)).
The tiny numbers are not necessarily part of the calculation of any problem. I would suggest that their purpose is simply to illustrate why the answer is correct. So, the tiny numbers do not need to be aligned with the equations in any way. They only need to be grouped together via formatting in braille (for example, by using blank lines) as they are via color in print.
I hope that helps. If you can share what you come up with here, we would love to see it!