Hello,
First of all, X2 is an EtherCAT interface not an EtherNet. It is kind of already coupled inside of the robot and to the controller which means you can not hijack it in between its connection.
Second, Robotiq gripper's EtherCAT interface is supported by LBR iiwa. You can simply import a device description file to Sunrise(WorkVisual is needed) system and control Robotiq gripper in your robot application-java code-.
Third, If you want a simple direct wires on the flange, you have X74, X75 which are directly bypassing the robot body and going out through X76 at the base of the robot. You can make use of that interface on your own. It has capability of 2 power inputs and 6 (3 x paired and shielded) lines.
Fourth, the last question regarding WV, is in chapter named "Bus Configuration". If you are looking at END user manual, ask an SI manual to your provider.
Fifth, if your device's interface is converted into EtherNet, you probably want to use KLI interface on the controller, right above the power switch. Yes it's the port that you use when you do installation and synchronization. I personally think it will be the easiest way to do it if you're well aware of socket comm. programming. Or to use an EtherCAT(Second proposal) would be recommended.
Regards,