You might also add the model number of the ENA and the firmware rev.
In the past, touchstone files were only defined for single-ended parameters. So saving meant saving the single-ended and then converting. Newer firmware allowed saving Sdd as a touchstone (under the understanding, of course, that it violated the rule of touchstone files being single-ended data).
You might need to save as a different format such as CITI file for you situation, if the firmware isn't new enough to support more flexible touchstone saves.
Uh...your S2P file is completely 0's. You might post a saved S2P file from single ended parameters.
I'm just guessing here: most of my detailed experience is with PNA, but ENA has almost the same functions. Some newer features of PNA allow very flexible saving formats; for example save Sdd parameters directly.
I don't konw if ENA supports the same flexibilty.
But for simulation, what system are you using? With ADS, you don't import differential, but only single-ended, and compute the differential result in the simulator. If you are using ADS, I can tell you a couple of ways to do that.