- point 1: A. There is such a person as mr. Goodweather, both in the mind of the sender as well as in the intended recipient.
- point 2: A. The caster has met a mr. Fairweather, albeit in the form of your impersonation. As long as you keep pretending to be Fairweather, Sendings from your fake Fairweather friends (see what I did there?) should arrive at your mind.
- point 3: Tricky. The previous answers are both based on the premise that a created identity is as real as a "real" one, but that just makes this question harder to answer. A and B are possibilities. I'd disregard options C and D. C falls outside the established rules for magic and D just creates more questions. My suggestion would be E: the spell connects to both Fairweathers, since they both are Fairweather, and "Fairweather" is one, single target (even though it's portrayed by two persons). This allowes subterfuge to go unnoticed for longer (which is a good thing in most games), and creates funny situations if both Fairweathers reply.
- point addendum: as long as there is a person who is, as far as you're concerned, "your friend", a Sending should arrive.
The above is 100% my own opinion - I don't think any actual rules cover this (rather interesting) situation. But really, the answer should always be: "Whatever is the most fun for the players and the GM".