Well looks like it works !
A little cleaning of the rust first would not have gone a miss....
What thickness is that metal ?
What size wire are you trying on it ?
The underside of welds can tell quite a bit about how well the weld is working (penetrating)
Well with that then on the higher settings you should be on the point of blowing through. Note the metal under the ground clamp is also rusty ! Which is not a good conductive path.
Well if you look where the clamp was clamping you may see a couple of marks where it has arced a bit trying to make the circuit. If the metal was clean this should be reduced and make for a better connection. The rust will also get pulled into the weld pool and cause some contamination to the weld.
Not sure what you mean by "would multi runs be ok today" ???
For a simple butt or lap weld on 2mm sheet you should be able to do it with a single pass, probably about 70-80A (rough guide is 1Amp per 1 thousandth of an inch of thickness, 1mm = 40 thou" so 2mm = 80 thou" or 80A). Multi-pass welds tend to be more for thicker plate or pipeline welding.
Looking at your snakes above I'd say your travel speed was generally a bit fast for the rate of deposition (how fast the wire was feeding into the weld) but in a couple of places you may have had the opposite (too slow travel, lots of wire = a high weld 'cap', not necessarily with much penetration).
Not criticising, I realise you were just testing the set