R.K.
Kids will drive you nutty if you let them.
I think the reason he puts everything in his mouth is because it is the best way for a baby to determine what it is. And yes, it's gross.
As far as his meals go only put a little on his tray at a time. One of two pieces of veggie, a small mound of whipped potatoes ect. leave the rest on his plate on the table or if he is not using a tray and pulled up to the table use a small bowl to put the food you give him and leave most of it on a plate or bowl out of his reach. As he eats a little give him one or two more pieces. Sometimes babies get overwhelmed by what looks to them to be large amounts of food.