MadProfessor,

Suggest you have a good look at the sticky at the top of the forum (BA Forum Dashboard (please take a moment to read this sticky)) and its associated links. Lots of FAQs answered there.

(1) See the sticky (the Executive Club changes sticky might be pertinent to your queries too)

(2) Individual legs. Depends if its a two-class or three-class flight. See the sticky for TP levels.

(3) Don't forget you need the BA metal flights in order to get your status change. Just racking up the points alone won't do you much good.