I don't think your info on Singapore Airlines Cargo is accurate. CH Aviation shows them as having 1 747-400 in the desert, the other 13 still flying.
Hardly "most of the fleet". As far as crew, I couldn't tell you. Maybe they are using -400 passenger crews for the freighter ops, but I think that would probably be more expensive than keeping the freighter pilots.
At Cathay & Dragonair, crew control is getting very creative in using guys cause they are desperately short. The CAD has even advised them to stop certain practices because they are illegal, like counting dead-head time as rest to be followed by duty.
