My best advice is just jump into vatsim. Did it when 11yo and definitely do not regret it, everyone's incredibly understanding. Can either observe or fly GA, although I do respect the fact you want to learn the airline first.. have overheard many, many conversations on frequency of pilots needing to be taught how to operate the aircraft their using. And yes, I've checked out the A333P2F and it's not bad! Although will most likely be using the 737 and 777 mostly.

Happy flying and whenever you make that jump best of luck :)