If a mage was Astrally Projecting from his positively aspected domain (say his apartment) would he get the bonus to his magic regardless of where his astral presence roamed?

No. His body remains in the domain, but he is elsewhere.

His body certainly would.

No, the important thing isn't where the body is, but where the mojo happens, so he'd get all the modifiers depending on what the background count is like whereever his mind happens to fly and cast around.

EDIT: Argh, too slow...

That's what I thought, just wanted to clarify because I noticed there is a Positive Lifestyle Quality that gives +2 to Technomancy skills while the PC is physically in their home.