- You replaced "pmclb" instead of "steve" with your namespace in the uninstall tag. ("steve:nitroxnova/uninstall"). This would cause the uninstall function not to be called, but you didn't use the function, so it has a very low priority.
- CustomName (of mob) is a JSON text component. Try using single quotes, since then you can just add double quotes inside without escaping (using the \). Soooo "\"text\"" would become '"text"'- You're right that UUIDs should be random, but you used the same one for all events soooo leashes might not always connect to the right mobs. Try generating new ones using a UUID generator for each of the events. Firing the same event twice still can mess references up, but nothing you can do about that.