Ugh yeah that is small. I'd say heat, salt can't hurt I always add it to my tanks after a WC or when introducing new fish.
Anyway I asked, my DH said he found the softer spot of his shell close to the underside and gave it a lil 'pinch'...I remember being horrified. But a few moments later out wriggles this little cray he flipped over onto his back stretched his legs and off he went to hide under his rock. I wouldn't recommend doing this unless you feel comfortable doing so but I've seen it done and my cray was about 1" when this happened. His head part was coming off but he couldn't get the tail part to break away.
Anyway you want your tanks to be around 74-76 F, I keep all my tanks in that range and have had no issues with anyone molting since. The original shed issue was caused by a faulty heater, tank was 66F! Poor guy had to have been freezing.
Keep us updated I hope they pull through this. I just read the insert about the dog chemicals, thats suck-o man. At least you know it wasn't the food, water chemisty or anything to that nature. Just an accident.