Is general admission on the floor for standing room only?

Yes, its only for standing room/people who want to be up closer to the stage.

We saw Kevin James and there were seats on the main floor

Yes

Yes. There are bars on each side of the floor.

Depends on the show, some are seated. And some are GA?

Standing room only

Floor is general admission, standing room. There's a wheelchair section, and there's also a VIP section on the floor in the back of the GA area.