The 100ah rating has to do with the amount of power the battery will hold. The 60 amp is the amount of current being drawn through the breaker. Apples and oranges! Use the 60 amp breaker and the 100ah batteries. As for connecting the batteries together, you want them in series, not parallel. In series, the voltage adds together (24v). In parallel, the voltage remains the same (12 volts) while the amperage increases.