Well, it was bound to happen sooner or later, heh. Don't worry too much .... legs, claws and antennas will grow back with each successive molt. So, light damage and lost limbs will be regenerated.
Anyway, I don't know about losing a sperm plug but I know they don't always take or aren't always good/fertile/etc. She could probably lose or remove it, too, I would suppose. But after mating, it should take a few days (or up to a few weeks) for her to berry. It's different for each species, each individual and each set of tank conditions. But they all generally fall under the few days to a few weeks realm (if you haven't seen anything by a month you'll need to reintroduce male to female).
Also, you'll need to find another home for the female or male, unless you want to wait on having her berried. If he is trying to mate, and not fight, he's just going to keep replacing his own sperm plug over and over and over again until they are removed from each other.
As for mating or fighting though, pretty easy to tell apart in most cases:
Ignore me in this photo, lol, but look at the crayfish. That's an aggressive posture... claws up or extended and the front of the body raised up. Crays that are fighting with approach each other in similar positions and then start trying to pinch, push, wrestle and body bump with each other until someone loses a limb, tail flicks away or goes into submissive behavior.
When mating, the male should just be approaching the female in a normal stance and then quickly manipulating her so that they end up in this position rather quickly:
The female also usually freezes pretty quickly in this process and doesn't do much movement. So if he's approaching her (even if his intent is to only mate) and she behaves aggressively rather than submissively, it's going to trigger him to fight.
I'll get a pic up later of them.
