2) Look into enet_sv/clsend_event() I think it's exaclty what you need.

1) Please don't let the community search for coding mistakes if the code has already that size. Try to find out what is executed before it crashes (use the debugger or use the error() function to see what was called before the crash).
But I would advice you to use enet_sv/clsend_event() instead of enet_send_string(). It would make your code much easier and cleaner => also bug searching will be easier then