How strict should one be with child?

there are more ridiculously bad behaved children today then ever. I don't want my child to ever act like that. He is a very well behaved child. We are very consistent with him. It seems like when we start being more lenient with him, because he is very well behaved, he takes that leniency and misbehaves. By misbehaves I mean he throws huge temper tantrums when he is told he isn't allowed to touch something he knows he has never been allowed to touch, or when its time to come inside from playing outside. He is almost 2 years old, we do spank him if he is doing something dangerous such as touching outlets or walking into the road. Otherwise we use a time out chair. He goes in the time out chair for one half hour. this seems like a long time, but the time out chair is comfortable and the time is enough that he usually is told to sit in his time out chair once a day or every other day. every time he comes out of the chair we ask him to explain why he was punished and to say sorry. This has always worked, except recently he has began saying that mommy (me) touched what he wasn't allowed to touch, or mommy didnt listen. I tell him he is the one who did it, and he repeatedly blames it on me. does anyone have any suggestions on how to parent a child, where they have respect and listen? What is too strict?