Hi Andy,
Did you save the fractured parts? Remember the fracture face appearnce on your Tie Rod? The small flat crescent at the origin of the break was the crack growth by means of Fatigue. If the CV fracture shows the same flat, bright crescent, fatigue is the cause of the fracture. If this is the case, a stock part could be smoothed, polished, and all aharp notches radiused with a rotary file and then the part could be shot peened. The resulting part would be no stronger, but would last as much as 10 times longer, if engineered loads were not exceeded. If you are jammed in a hole, engineering loads go out the window, so a bigger unit would be nice. Polish and peen still applies for fatigue resistance.
If you have the fractures, I would like to have a look.
Roy