Nadine - I agree with your interpretation of the WPATH definition as it fits us... It is a very broad umbrella, I agree, but some definitions are like that, and it's barely different to being categorised in other ways.
Jennifer - Aren't you confusing and mixing gender identity with sexual identity? Your sexual identity is physically fixed, as for most of us - but your gender identity is not just (or even) your physical form; it is what goes on in your persona and is about who you are.
Correct me if I'm wrong, but you struggled with an internal conflict regarding your dressing for many years until you just had to come out your SO and you also had a real need to take your feminine side out into public... if that isn't a sign of even mild gender dysphoria, then I don't know how else you'd explain it?
I don't think there's anything wrong with that - most of us have that need or desire to a greater or lesser extent, the only exclusions from the trans* category would be the purely fetish-dressers, who are possibly just as difficult to categorise.
I honestly don't think there's really a benefit in the category unless you got to a point of requiring some form of legislation, but I think that would be quite tricky to get acceptable definitions for.
Katey x