The buffer selector is not really used for that function. It is a simulation tool to grab certain signals (from the different signal iterations) generated in bidirectional or loop simulations. I would suggest going through the bidirectional tutorial:
Lesson 5: Bidirectional Simulation — Working with Multiple Iterations
I left in the first splitter in the attached project because the simulation still works, it appears through that there is too much loss so the thermal noise at the receiver is making the Eye diagram unreadable. Again some of the things you were missing here like Initial Delay are ideas that are explained in the tutorial.