I think you are fiureing out that tack welding may have been a good start if you have some rigid angle or extra tube. Clamp the assembly into submission and see if a few tack welds hold and straighten it out. If this does not work than reconsider cutting and refitting or if you are careful...
You could take it to a tech school let a student get some torch practice make it big for error sake and make a donation to any welding or fabrication clubs they may have win win.