It's such a hard transition from babies to pre-schoolers. This is what developmental psychologists call the age of autonomy. He is becoming his own person and for similar reasons likes to rebel like teenagers do. Fortunately at this age - you have control and you can use every one of these situations as a teaching tool to make him a wonderful, productive and caring person.
The best thing that you can do is develop a behavioral modification plan. Everyone has methods that do and don't work for others, so go to a book store and skim through a few that you think would work for you. My favorite and the author who I think has a great philosophy is Tracey Hoggs (The baby whisperer).
As for now, your son needs boundaries and appropriate consequences for his actions. Children need consistency or they become confused which can cause them to act out even more.
Set up a time out system. It should be one minute for every year old he is (so 3 minutes). If he gets out of the chair, or has a tantrum the 3 minutes starts over. Eventually he will learn to calm down sooner so he can get out sooner which is also a good way to teach self-control.
When he says things like "I hate you" remember, children don't have a TRUE concept of love, hate, etc for a few more years. He has just learned that this makes you upset. You should do the time out for back talking and then when he is calmed down and you are calmed down explain to him why that hurts your feelings. Something like, "mommy loves you and takes care of you and she wants you to love her too. When you tell mommy you hate her, it hurts her feelings". Then continue to tell him more appropriate ways to explain what he's feeling. Say, "It's ok to feel mad or upset, but that is what you say instead of I hate you. Say, 'mom I am mad because you took my toy'".
He may seem too young to understand some of this, but just like reading to an infant, the sooner you start, the more innate this becomes. Good luck!



