Imagine you're in a strange world that you've just got used to when all of a sudden that world is turned upside down, you've been taken on a bumpy ride and you couldn't see what was going up, picked up, prodded and pocked and put somewhere completely alien to you with new sounds, smells and sights and THEN this large creature keeps looking and you and picking you up even when you try to hide and you don't know what's going to happen next but all you can do is try to protect yourself in the only way you know how! Is it any wonder this poor little stressed out snake is biting you? He's scared witless!!
Give him at least a week before you attempt any kind of handling whatsoever. The only time you go near that viv is to change the water and even then you do so with the minimum of disturbance to the snake as possible. Otherwise, that snake is becoming more and more stressed with less chance of keeping a meal down and an immune system that's becoming reduced. This isn't a puppy who thinks that the world is automatically going to love them - this is a snake whose natural instinct is that it will be eaten!