If you read http://gwan.ch/faq#listener you can see the answer. If you want to use on gwan server instance, just use /gwan/0.0.0.0_80/$abc.com The 0.0.0.0 will listen on port 80 to all ip addresses set on your system. It's the simplest and most flexible solution.
But why do you have 3 ip addresses for the same domain? Normally this is used when you have three different server answering on round robin, or other high availability configuration...
And you know that ip addresses end on 255 right ;)