If he's hissing then he is scared and telling you to back off. Also if he's 3 yrs old then he probably has enough reserves to go a bit without loosing too much weight. He is stressed from the move aand going into shed. Think of it this way. You are blindfolded, and put in a strange room. There are people and things touching you that you can't see. You would be stressed too. Give him time. Make sure you keep fresh water for him, and his parameters are right. When he's done shedding, and he takes a meal or 2 then start handling him a bit. My girl had not been handled for almost 2 yrs. She started hissing at me when I went to pick her up one day. I didn't pick her up, I just gave her fresh water, and made sure her parameters were good. I didn't touch her until she got her eye caps off and she ate 1 meal. I did have to soak her to get all the stuck sheds off but that was after she could see again. She is now calm and happy.