How to find the normalized coefficients?
I'm not sure how you define your normalized difference equation, but in any case you can equate the $b_{ij}$ coefficents in the sos matrix with your $c$ coefficients, and the gain that tf2sos returns would then be your normalization constant $b$.

I think you already know, but just to be clear: every row of the sos matrix contains the coefficients for one second-order section, starting with the 3 numerator coefficients, and then the denominator coefficients (the first of which is always 1). You can incorporate the gain into the first section.