It seems to me that you are doing everything right. You configured the router to let the port 4000 go through, and also configured the router for the UDP port (if I was you I would try to disable UDP in the beginning and first ensure that the basic connectivity to the TCP port is OK, since this is what you essentially need). What exactly is not working now? Are the IP addresses correct? Can it be a firewall problem on the receiving machine?
About the documentation, maybe you are setting your expectations too high. We can explain how to use the software (that basically it is a matter of connecting to port 4000 and inserting the username and password) but you can’t expect the documentation to be a port forwarding and NAT traversal manual dealing with every possible router, firewall or network setup. Every software in this category provides a global directory and automatic NAT traversal. Without this is impossible for 99% of the users to deal with the required network configuration. I know you are knowledgeable enough to do everything yourself, but not all users are experienced network administrators or firewall specialists. We are obviously working on such automatic NAT traversal. While the software is hopefully good today for a corporate setting where there are professionals paid to solve this kind of configuration problems, at the present moment I would never suggest it to the wider consumer public. Probably you noted that we are not even trying to advertise it to such a audience. I don’t think extending the documentation would be of any help.