Welds in the first pic are good, I like them. (second reading, oh the fab shop did those? explains that.)
Other pics look like you're stepping too quickly. It's gotta wet out at the toe of the weld more, so it doesn't look like wagon tracks. Basically just watch your consistency and timing, and watch your weld puddle. The beginning of a weld is going to determine how wide your bead will be at the end.
Third pic from the bottom, bring your welds around more to meet the tie-ins and melt them in.
And heat register at the back of the material doesn't necessarily mean you got good penetration, but beyond cutting and etching yeah it's the best indication you're gonna get other than just the feel of the weld when you're burning wire.
And with that size of material, you shouldn't be dropping voltage at all. "Get it hot and penetrate."
"Chilton's and Haynes are for brake jobs, oil changes and starting campfires." - CJ7-Tim
'98 2dr/5spd Cherokee rockin' on tons, 5.9L V8 Magnum, HP60/14b, 5.13:1, locked, 14" coilovers, Dana 300 4:1 twin stick... oink oink!