A picture would help.
Is the prod a "solid" glass limb no wood or foam core?
if it is possible to split out, that would be my preferred starting point as it is often very difficult to run any glue into the often invisible and impossible to wick glue into hairline crack at the very end of the split. A split that hasn't separated will probably have intact material, impossibly finely fissured section, and then the visible crack. Even watery crazy glue won't penetrate everywhere, and doesn't hold in my experience either.
The closer the crack is to the neutral axis the easier it will be to repair. If it runs out to the surface anywhere, you probably can't easily restore it to health. Depends how motivated you are, but you would have a de-lamination, and cross fiber blow-out in that case.
Before there were so many crossbows, and there were so many different types, it was easy to get a standard recurved prod. I would look into that:
I got off down an internet wormhole a while back and was looking into making those euro style competitive crossbows, or at least a fun version of one. They have them for shooting at 33 feet, and 99 feet. Anyway, through that process I did find info on making serious X-bow limbs, so it is out there on the net.