#5 is the pic that's bugging me. I've never used a spray MIG, but the weld looks cold to me. Prep is huge IMO for MIG. Grind the mill scale off to start with. Bevel the end of the piece you're standing up.

Out of curiosity, why did you get a spray MIG? It's not the typical homeowner MIG. I've got miles upon miles of wire behind me doing custom off road fabrication and it's my understanding that the spray setup is for heavy welding.