In my experience
1. These birds are doing well in large aviaries. (well the ones that I visit anyway)
2. If your aviary is built well enough then the birds should be able to get away from the draft.
3. Supplemental feeding should be a part of normal diet.
4. You cannot compare what we do in Australia to the rest of the world. Especially in the northern hemisphere breeders have internal flights that must be heated due to the much colder climate. This can also vary from state to state even in our own country.
But I have heard that some of the better overseas breeders have birds that cannot fly properly for the very reasons you outline.