Tell that to Shlomo Carlebach Z”L, who often whistled (and so beautifully, with such heart) when he sang in public. Goyim eat and sleep, too. Should we give those things up?
As to the hand folding – I have heard it is how the Goyim hold their hands when they are in church, so I could see that, I suppose. I will say this, when I went to Crown Heights Yeshivah over 50 years ago, our morahs and rebbies always taught us to sit up straight with our hands like that during quiet time or when someone choshuv was coming into the room.