Your symptoms of physical illness make sense, ignore people bagging on you for that. Some of them are also probably psychosomatic, so try to calm down about this whole thing. Also, if you play the game with a regular schedual then your suffering from a mild withdrawal effect due to the lack of expected brain chemical release that your body has become accustomed to over the last three years. If this is the case its probably a dopamine issue. Should clear up as your body chemical re-adjusts.
Those are the three main reasons people get banned and you clearly did one of the three.
Unless he was hacked. In which case someone who stole a part of his identity did one of the three.
You might run into difficulty proving you were hacked although i suppose if the access came from a computer you never use you can try and point to that.
I suggest if you do go the litigation route you threaten to sue and then asked that it be settled out of court by granting you your account back with a different passoword and possibly name.
Keep in mind that seeminly petty cases against giant forces can be won. I read about a kid who sued the school for being suspended three days after he gave a mildly suggestive speech. He won damages equal to three days of teachers salary but the school also had to pay thousands of dollars in his and their own court costs.
And come on, it's a video game!
If its a game that charges 15 a month to play then the company just took more than $500 from him and kicked him out the door without even telling him why.