Do you need more then one?....No, however ackies are heavy breeders which reach sexual maturity at a young age so you might want to look into that.
All the other questions you should be able to answer yourself.
Can you take it places? Well if you choose a calm one out of the clutch you probobly can. If you choose a scared one you probobly cant.
Will it eat at the same time as you sav? My guess would be that it will eat when you put food in its cage.... thats just a guess by the way.
Will it eat as much as your sav? Most living organisms can only eat until their stomache is full. Ackies are much smaller lizards then savs with much smaller stomachs so.... no. If you couldn't answer that question then you should study the acanthurus monitor a whole lot more before you purchase one.
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2.2.1 Bearded Dragons
1.0.0 Lemon Pastel Ball Pythons (NERD Line)
0.0.1 Water Monitors
1.0.0 Pastel Red Tailed boa Het. for Albino
0.0.2 Yellow Ackie Monitors
And Counting...