You have hit the Nail on the head,he has feelings of jealousy,best to ignore the negative stuff he says it is getting him the attention he is seeking, make sure he believes he will still be part of your lives and tell him all the ways he can help with Baby, he doesnt mean those things hes just acting out to get you to still be interested in him. Tell him how much you are glad he is goingt to be able to help and be a big Brother, he needs reasuring from both of you that he will still be important in your lives.It is pretty normal, when the Baby comes make sure he is part of it all and not feeling left out as so often Babys come along and older children get left out and feel bewildered at being Usurped. The fact you came here to ask shows you care lots of talking about him, you guys and the Baby and let him help when Baby comes. Good Luck
Sorry, this was a double post..