- At the start of your trip did you pack it cold (40F) or were the contents closer to room temp.??
Really it looks like your refrig is performing as designed.
The spc for a NC751BB is 3.6a at "12" volts. 3.6a x 24hrs means a 86 a-h used per day. Your 200a battery can supply 100a of usable amps (50% of rating). So you should expect at 72F ambient 100/86 = 1.16 days of use ...or 28 hours of use to drain your battery (id: 12.9v down to ~12.1 volts).
To get down to only a 2.2a draw like you referenced would require something like a Isotherm CR-130 that costs $1,300.
Another comment you made was bought the refrig compressor turning on for 1 minute and off for 7. The refrig on/off cycle should be say 10 minutes on say 20 minutes off or something like that. 1minute-7minute implies to me that the compressor is stalling (low battery voltage), overload protection shutting system off for 7 minutes to cool down from the stall and then the refrig trying to turn on again but failing. Again normal on/off cycle is much longer. My refrig (different brand) cycle is 3 minutes on then 10 minutes off.