[shergry]

The lower the guage number the higher electrical current it can handle.
Yes, there is a serious problem. Hope you get it fixed by a trained electrician.
When the inverter is on and the shore power is on is there is a safety feature that disconnects the inverter so that shore power does not feed to the output of the inverter? Example: just as a generator has a tranfer switch. Again, just asking berghild.