Wow, way beyond my skill level pugs, but I realized I did not know anything when I went to my first metal meet years ago after the second metal meet figured leave this work to the pros.
I feel funny even saying this to you with your skill level.
Something I was taught in the early 70s is when making gaps on a door like you did is, use a brazing rod start heat at the top, and maybe every 4 to 6 inches to shape.
Then melt in the whole distance and mark it, and sand with 80 grit by hand.
You may know of a drawback to this, but I've never seen any, and it is very easy to form and sand.