If your difficult child is on the baseball team, then he has no choice, he has to go! His team mates are depending on him! If he says his anxiety level is too high (and you're sure he is lying) and refuses to play, then he shouldn't be on the team. However, I would let him know that his X Box isn't going to be his constant companion. Maybe once he learns that his X Box time is going to be limited, he'll suddenly begin to feel much better, even be able to play ball, lol... difficult child 1 used to use similar tactics with us. We had to remove his computer from his room once he used up the allotted time. If up to him, he would have been on it 24/7, leaving it only when he had to use the bathroom so badly that he was doing the pull-ups "potty" dance.
As far as the school dance, I wouldn't force the issue. If this is an activity he usually enjoys, then maybe there is something bothering him. The teen years are such a tough time socially even for TTs. If at all possible, try talking with him about his feelings. Even if you get nowhere, you can let him know that the X Box will not be used as a substitute for social interaction. difficult child 1's psychiatrist used to tell difficult child 1 and us, that difficult child 1's computer was his "girlfriend." He used to say this in such a joking manner, that it even got difficult child 1 to smile (tried to hide it though!)
Keeping my fingers crossed there are no major explosions in your house over this... SFR