didnt look too deep at all of that but instead of all those branches you could use a select node.
create a function called IsCorner() which returns true/false plug it into the select node and then output the the class you want to spawn there.
to determine a corner you can use some math, on the grid macro you have the x/y so you know the corners will be at index (0,0 0,x 0,y x,y)