Ok the 12 volt connections on the Yahama are more or less useless,
Your problem is too much converter.
You have 1,000 watts PEAK. running wattage is not that high. (do not know the precise specs on that unit) the old Yahama 1200's could produce 1000 watts long term (1200 peak) I think you 1000 s 870 running but may be less.
My Progressive Dynamics 9180 draws 1,000 watts. More than your Yahama can produce long term. IF THE BATTERIES ARE LOW
Your Fridge draws 300-400 Watts You are now officially in overload.
So there is your problem
Options
If you can "Throttle" teh converter and slow it down it will draw less. my 9180 for example is in the 100 watt range once the batteries fill up.
Kill the fridge (lock it on GAS) may help if the batteries are not down TOO far.
Get a Yahama 2000i
