Hehehe, you guys crack me up.
I've reduced it down to two very short paragraphs... sticking to the facts. Here is the basic idea (I am using more proper language, of course, in the real message):
Paragraph 1: sorry, but I didn't sign anything, and I'm not paying anything. I told you I had to talk with my fiance before deciding. This is SOP for wedding photography.
Paragraph 2: both the interview and e-mail you sent did not request my signature, nor were they legally-binding. I will not pay you.
That's it. I am feeling better about the shorter version. Thoughts?
On the side, I don't know why this is so hard for me. I guess I am very wary of committing anything to a written form, in case it will be used against me... this whole thing is giving me an unexpected level of anxiety.