1) Coming to you when called should feel like he just won the lottery. Give him treats, make a big to-do, really high praise - if you don't feel foolish, you're probably not giving him enough praise. Make sure to call him at random times. If calling him to you usually results in fun time being over, there's a disincentive to come. And of course, never call him to you when he has done something that you are going to scold him for - coming when called is always a positive experience, no matter how frustrated you are with him.
2) His prey drive may be a little weak at 3 months. Use treats to encourage him to go that last bit. I find that most dogs will do cartwheels for bacon bits. Try treating him to get him to return all of the way. When he gets a little older and the prey drive is a little stronger, you can back up as he approaches you with the ball. This will help him to bring it all of the way back to you.
HTH