rv refrigerator

I have two house batteries that one has 975 cranking amps and the other has 675 cranking amps and my starting battery that has 900 cranking amps.Only one has the reserve on it and it says 135.how long can i run my refrigerator on these batteries?I cannot turn my disconnects off becouse the frig goes off even though its on gas.Will i get up in the morning with dead batteries?