bad 3 year old

MY 3 yr old grandson has run amok. His Mother is a single parent and my husband and i watch him while she works. She is a 2nd grade teacher. At first we thought it was the terrible twos but... when he comes in in the mornings he is in a bad mood we figured because his mother had to go to work, after a short time he demands breakfast and if he doesnt get what he wants he screams and throws a fit. He constintly tells us and whom ever else is around thet he doesnt like or love us and doesnt want us around. He has started hitting and punching his mother when ever he gets mad , we have spanked, made him sit  by himself or go to bed but he just gets madder. We are all  about to give up. Please help.