Have waded through this Torque Arm discussion to see if repairs were made on OP vehicle. Pardon me if I missed it somewhere.
Concerning the 110 welder-they do not have enough "beans" (amperage).
The base metal is more than likely an alloy that is coated (dipped) with rust preventative (most likely a proprietary galvanised solution) and then painted.
I would not recommend heating with torch as it possibly could weaken metal beyond affected areas.
It is necessary to grind through the coating to get to good metal for welding.
In looking at the pics, it did not appear that the welder had any sort of protective gas around the heat affected zone (HAZ) to protect metal while cooling. He could have been using fluxed wire which is nasty to work with, leaving lots of splatter.
Having said all that, it is necessary to use 220 Mig with either 75(argon)/25 (CO2) or 100% Argon shielding gas.
Welder might to experiment with different filler wires to determine correct for alloy. But any good body shop should know correct number.
Recommend welder (and owner of vehicle) consider a little "gusseting" on replacement parts, if it will pass tech.
Sorry if preaching to choir here.
Tom