The previous fractures lead me to believe that the rod was badly bent at some point in the past, then straightened, sort of, cold. That damage, plus the flexing since then have made the rod brittle. Welding would repair it for a while. Any flexing would cause it to break again. Other than replacing it entirely, replacing the majority of it- the center section-- and welding that to the existing ends, are about the only good choices available. Long sections of the same diameter will last longer as having part of it larger simply means that the majority of the flexing will occur in the shorter smaller sections and they will become brittle sooner.
Luck favors those who are prepared