Change the square wave AC balance control to maximum penetration ie 64% time at negative. Discard the Green EWP Pure tungsten for Brown Zirconiated or the newer Gray/Orange Ceriated or Black Lanthanated tungstens. Some pure tungsten will split or flake when welding with Square wave AC.
Use a tungsten electrode amperage capacity chart to determine the amperage limits of the tungsten type and its diameter. From "D" increase the tungsten diameter one size. ie 3/32 increase to 1/8 etc.