Its easier to show a screen caps to show what info you should have in where.

First of all for your domain check that your IP address is shown correctly and that you have passive mode set.

Setting the port forward range in Serve U

Now we need to set up a port range for the router to use.

So from the local Server Settings go to the advanced tab, and type in the range of ports which Serve U should be listening on.

I've used 52000 to 52010 and your screen should look like the following:-

See next page for router configuration.