NOT giving you legal advice, but here's my question: Why don't you want to tell the nice lady at the embassy your true story? Is it because it's personal and possibly embarrassing, or because you think that it will make your relationship look less real? The reason I ask is, if it's in any way the first reason, just put that aside. Do and say and reveal whatever you need to to have your best chances of success.

With that said, especially if you think that the kink will somehow detract from the legitimacy of your relationship, I would include the correct dates and information, but in a neutral vanilla way. You met on a social networking site due to shared interests. In time you learned that you had much more in common, became close, finally met in person and spent a great deal of time together. Present as much of the vanilla details up front. Then, if you're asked, you can reveal what you need to to corroborate your story, including emails etc, so long as they are in the context of the larger relationship you've already provided the evidence for.