Personally I think I would just cut the SFC free with a cutoff wheel or air body saw and line them up again and re-weld.... the offset heat thing can get really tricky if you dont know what youre doing....it could even make it worse,or just make a bigger weld that you may end up having to cut free and reposition the pieces anyway.
Heat in sheetmetal can move thing alot....... lesson learned....fix it and move on.