high drain lead acid battery concern
Based on above comments if Costco does not have detailed specs for the Kirkland battery, then you need to test the batteries.

80A per battery may cause H2 outgassing so use in a ventilated area.
1kW = 80A * 12.5V   

Although it may work. Your test results are the best bet.  No obvious faults except a worn out cell.

Ensure you have the proper charge profile as AGM types need temperature compensated voltages.