I agree that you should take him to the vet, and if he's not neutered, then that would be the wise thing to do. If he already is and there's nothing else wrong with him, then you need to start treating him like a cat. Having an animal around your child that bites and scratches is unacceptable. You need to make sure that you do a couple of things:
1) Make sure to teach your daughter to be gentle with the cat. It's good that she'll defend herself if necessary, but at the same time, animals, esp cats can sense rough children, and either they'll avoid them like the plague, or happily react, and how he reacts to people, esp children now is going to set the standard for how he behaves his whole life. Plus, if your daughter learns to be gentle now, she's less likely to have bad experiences with animals later on.
2) Do not put up with this behavior from your animal. Animals will behave like children-badly if you let them get away with it. Try keeping a spray bottle around and watch the cat. Do NOT let him play with your daughter's toys-at all. If he goes near them, spray him with the water bottle. If he thinks he can play with them at all, then he'll believe he has some sort of right to them. Animal logic is pretty simple. If he approaches the toys while your daughter is playing with them, spray him and speak sternly. Don't worry about traumatizing him-this is effective aversion therapy. Make sure that he has his own toys to play with-keep them in a basket of just his toys, and gently introduce him to them-make sure that your daughter does NOT play with these.
It can be frustrating dealing with animals, but it's really important to keep in mind that they are animals, and your child is most important. You need to be the one in charge and establish boundaries, and both the cat and your daughter are the perfect ages to start setting those boundaries. Best of luck!