well done on two counts - your tennis win and ending the bullying problem. I'm racking my brains on why your son is being destructive sometimes and a couple of things spring to mind.
Is he someone who has to fiddle with everything? I was like this as a child and so is my oldest son - he tests things out, can't put things down till they break - some of my son's friends are the same. Very irritating - it's not as if he has malicious destruction in mind but things just happen. I do as you and punish, or try to stop the fiddling in the early stages when I catch it.
The second thing I thought of was attention seeking - you say you spent a whole morning playing games with your son, but perhaps he just did not want it to finish. I don't think the answer is to give even more attention when this happens and you were right to send him to his room when he was bad. Your son has to learn that all games come to an end and you have to do some things without him. Can you look at how frequently you warn him you are about to leave him alone? perhaps you need to spell it out more and let him know when he will have your attention again. If he is well prepared for your absence, he might come to terms with it better. And follow up by saying you expect him to be good while you are off doing your stuff and if he isn't you will be cross, and the stuff you are doing is for both of you anyhow.
Hope he came downstairs in a better frame of mind!