Not sure about #1, although the drink prices in the casino are rumored to be cheaper...
#2: No, only on Carnival, although if you position yourself where the crew can see you you might not get many objections .
#3: 2 main restaurants, Windows and Garden. I think there are three specialty restaurants now. The cover charge is usually 25/pp, but there are specials almost every night- 2 for 1, early bird, etc.