Re: outbound
Between J food and Galleries food, I'd pick the latter, seeing that the choice and quality have been spotty at best in J. If you don't like the fare in the lounge at least you'll still have a back-up (such as it is) on the plane.
Re: a taxi to the airport
I've always taken the airport train from Hongkong Island, where you can check in your bags the morning of your flight, then have a bags-free day to do last minute shopping and have a nice dinner before going to the airport.
Because of the 2 BA flights close together, the CW lounge is indeed a horror because of how crowded it is. A quick look for curiosity's sake is ok, but I'd spend time in the CX lounge.
Have a great trip! (And write a trip report

)