Recommend you to read some parenting books like:

The happiest toddler on the block
Parenting with love and logic (I did not read this one)

You can find these books in your local library. After reading those books, you would have better idea about how to deal with your two-year-old.

You need use some techniques when your kid refuse go out of the tub. Maybe the bathtime is too much fun, he really wants to continue his play.

Strategies:

1. Tell him: 10 more minutes, we are going to finish bathing ok? And then give out 5 minutes, 3 minutes and 1 minutes warning.

2. I just switched off the light and close the door and tell him he can come out when he is ready.

http://blog.wenxuecity.com/blogview.php?date=200802&postID=19395

About discipline, try distract his attention and say something like, book is for reading, we do not tear book apart; fork is for eating, we do not use it to play etc. Say more positive things. State what he can do rather than say what he cannot, he would be more happy.

I know you feel upset when you son says something like I don't want mommy. They might mean it at the moment but you know that he would always want you. Let it go and keep telling him how much you like him and admire what he did. His ability to wear his clothes, help you out etc. Little people love encouragement so make sure you give plenty of that to him.

Do you have the ebook "Give me your hand"? I have the Chinese version. If you don't have it, QQH me your email, I can send you a copy.

Good luck.