Grizzly will take care of that not flat table. Even their catalog shows their milling equipment to flatten tables that come from the factory less than perfect. They acknowledge 'stuff' happens.
As for the miter hitting the 'back' or rip fence holder/gauge, that is a major gripe all of us G0555 owners have. Why Griz does not redesign the unit to lower that just 3/16" is a puzzlement. I have learned to live with it, but, like having a nagging wife, not happily.
"Folks is funny critters."
Think for yourselves and let others enjoy the privilege to do so, too. ~Voltaire