- Making a BA account is probably the best way of checking oneworld availability. Beware sometimes it shows phantom availability, though - you have to verify by calling.
- I would certainly not take QR old F over EY any F (new or old).
- The 2am-ish flights will basically involve eating in the lounge and sleeping as soon as reaching cruising altitude, unless you make yourself stay up and eat/drink (which, to me, is counterintuitive to flying F). Day flights would be much better for the eating and drinking, and the menu will also be more extensive since the first service on those 2am flights will generally be a snack service.
- As to whether you should use them now or wait for the A380 availability, surely it depends on how easy it would be for you to get those 80k miles again. In many ways, the A380 would be better enjoyed on a longer flight to the US or Australia, which is admittedly more expensive but also means you have a meaningful amount of time to eat, drink, sleep, enjoy IFE and so on.
To me, the European flight block time of 6-7 hours means non-stop sleeping on a night departure, and eating/drinking with just enough time for a snooze on a daytime flight. The flight really needs to be 10h+ to fully make use of the services without "staying up all night".