I've managed to get port forwarding working apparently, however this creates a new issue that I've not been able to find any more information about. When a person connects to my server because of the forwarding their IP address is set to a specific number, I presume the IP of the router itself? As a result of this I can only have 3 people connect to the server before the max-connections setting kicks in and starts refusing any new connections. I've tried changing this to the max number of players I'd want but whenever I start a new server this setting is reset to 3. Not sure if I messed up part of the port forwarding, or if there's just nothing I can do. Any suggestions would be helpful.
I'm not having any crashing issues fortunately. I might have fixed the issue though. While starting a server resets the max connections setting to 3, if I go and edit it after the server has started it seems to work ok. That or it's just hit and miss if things will work or not, which is a bit of a pain, but at least it works sometimes.