My sav was the same when I got her 4 months ago. I done the same and handled her every night with no great benefits then I STOPPED handling her for 2 months completely to give her more time to establish herself. When i offer her food i let her get a hold of it and then gentlty stroke her back for a while. Now she has calmed down completely and i can handle her no probs but occasionally she`ll hiss when i bring her out but the tail whipping and the biting has completely gone.
My other peice of advice is not to hand feed your sav but instead use tweesers or forceps because they are very intelligent and spot patterns quickly and the quicker you can stop your hand being assosciated with food the better. When i bring my tweesers out she knows its feeding time, meaning she doesn`t charge me when i go to clean her cage or her water bowl.
Hope this helps as this is only what worked for me, other people will have different advice.
All the best