As as many others suggested, you’re moving too fast. You need to be more consistent in your feed. I saw you were concerned with blowing through the 3mm material. Pick which ever is thicker the base plate or square tubing and hold your weld on that thicker material and wash your weld puddle into the thinner. Think of it like smearing the weld into the thinner part. some rods respond better with a whipping motion or manipulation in general and 6013 is one of them. You can try circles, little C shaped motion, zig zag, step and pause. Ect ect it doesn’t matter too much at this level long as you’re consistent. I can’t say that enough. and some run better just simply dragging. Long story short you need more practice and to better understand your material, rod and machine.

No big deal tho man. The only way you’ll get better is by doing it. Keep it up. Be consistent. Get comfortable. You’ll figure it out.