How many Ah

Ok so the batteries will be Lifeline AGMs probably the GPL-31XT, I was thinking of starting with two. The fridge is energy star rated so maybe figure a 50% cycle rate? Sounds like I better figure for 24 hours between charges.

If you mean energy from a 12 volt battery, conversions from 120 v to 12 volts will mean ten times as much current.

It will require at least ten times as much current from a 12 volt battery to convert to 120 volts
fridge 1.3 amps @ 120v for 48 hours AH = 1.3 x 10 x 48 = 624

electric blanket 200 watts @120v 8 hours
200 watts at 12 volts is 200/12 = 16.67 Amps. AH = 16.67x 8 = 133 AH

The fridge and the electric blanket won't generally be using their full rated power all the time; the electric blanket of course depends on what setting you have it on, and the fridge cycles according to its thermostat. The fridge probably uses somewhere in the neighborhood of 1 kWh per day, assuming it's a compressor fridge, or 2 kWh for the 48 hours; and the electric blanket...well, who knows, but 500 Wh might be a good guess, or 2.5 kWh for the two of them. Computer and especially cell phone charging are small loads in comparison.

3 kWh at 12V is 250 Ah, and conventional widom says you should avoid discharging lead acid batteries below 50%, so I'd say a minimum of 500 Ah if you aren't talking about lithium batteries. Six GC2 golf cart batteries would be one reasonable setup (with a bit of margin). That's just a quick, back-of-the-envelope sort of estimate; better would be to measure your power consumption with something like a kill-a-watt meter and work from there. Adding maybe 15-20% for inverter inefficiencies is a good idea, too.

If the fridge is a thermoelectric (peletier) unit that runs continually, it would consume its 150 watts all the time, or about 3.7 kWh per day. You'd be looking at a pretty substantial battery bank to keep it running for 48 hours.

At night probably low 40s and day time 70+

What is the ambient temp?