1. Yes.
2. Yes you can you 2 USB printers. Search posts of user "trebron" for more info.
3. I'm using an old Epson laser printer (which has no USB port) on my wl-500g deluxe with a no-name USB2Centronics cable, works without problems (for me).
4. Dunno, check the Hardware Compatibilty section in the forums here.