Flew LHR to Houston last year with BA (B747) with a total pax count of 4!
Wow - how many cabin crew did you have ?
Realistically economy is economy, a few little variations
I'm not sure, most US carriers you will pay for refreshments and headphones.
Id say Virgin or BA - With Virgin you will get free alcohol, refreshments a good entertainment system and guaranteed 4 engines for a while (which my wife likes - silly I know)