as you may have noticed, the angle changes when you cut off the bottom of the stem. sometimes you can just fill in but the fit is better if you re-cut after shortening.
I always put on a bigger foot. I just cut one out of steel plate.
I always leave the battery connected because it acts a a spike suppressor to soak up transients. removing the battery does not disconnect or remove all the important electrical parts from the structure. the battery can soak up huge transients with no damage. the most important part is to have a good ground from the welder as close to the work as possible.