To answer some of your remaining questions, the lounge for you on the outbound will be the EK lounge in T3. It's pretty good as these things go.

In terms of crediting your miles, the logical choice is of course EK, since you get miles and status credit for all your flights. QF is a poor programme, especially if you don't fly to Australia a lot. Crediting your return flights to BA is an option QF metal/QF flight number if you are going to be doing more OW flying later in the year. Note that for any BA status you'll need four BA metal flights during your membership year.