i have only worked with store bought fondant from a specialty cake store. the only time i have seen cracking is when somebody has stretched the fondant to fit over a cake. ... what are you using to prevent the fondant from sticking to the rolling pin and counter top? powdered sugar? crisco? cornstarch?
what formula are you using? sounds like you are working it to cold and dry.
i like to use marshmallow fondant for smaller cakes and Satinice for the larger cakes.
try using a brush to dust corn starch on your surface before rolling.
(not just broadcasting by hand).
bake first, ask questions later. Oooh food, my favorite!