There are a number of ways to take out spot welds one is to drill them out, then weld them up. The big trick here is to put a piece of copper behind the hole this acts as a heat sink and as a form so you don’t make a bigger hole. This is a good place to practice as it won’t show unless someone crawls under to inspect and if they do you will know the rest passed their test. Hope your thumb is ok. Keep us posted on the progress.