You're on the same route as me and booked through BA. We've had three flight changes and a change of equipment, but for us they have been of little consequence. I have though done a voluntary seat change for my wife and I, have you tried doing that online? I used the Malaysian Airlines site to access our booking, navigating through - Plan trip > Manage my booking > Select services > Choose your seat. I didn't notice if there was a meal option on the site but assume that there will be. I'm GF too, but will not bother ordering a special meal, there seems to be a wide selection of stuff that I can work around.

Apologies if you've tried that.