I doubt that will fix your problem. That thin tin cap will only keep the grease in place. I left that retaining ring off my CV's long ago.
If the axel is the correct length and the end stops are on both CV's the guts of the CV will not get near that ring.
Just to be sure what is going on, when you get the new CV, shorten the contorl arms as much as they will go. Grab the shaft and see if you can feel the axel hit the stop. If you can feel the axel hit the stop, drive it and I'll bet it will not pull apart.
Alingment will decide if you need to lengthen the control arm. If you do need to lengthen the control arm, you will need to add that length back in to the axel by either flipping the cages or adding material to the end stops.