I would say he has to go to the taster days. Nothing to lose there and he might find he likes it.
As there’s nothing wrong with the current school I wouldn’t make him move if he was against it.
I’d sit him down and explain that you and his dad love him and want the best for him out of life and you’ve been thinking about how to help him achieve that.
I would say that he has to do sport/another activity at least 3 times a week. As money isn’t a problem I’d let him pick within reason. Have a good look around and see what options there are in your area, so not just football/swimming, maybe rock climbing, paddle boarding or even paint ball/laser tag if he likes first person shooter games? They are both really good exercise, plus good for hand-eye co-ordination & team work with capture flag ones. There’s all sorts of activity out there and it doesn’t have to be “boring”!
Education-wise, maybe there’s a games/app design course he could go on or you could find someone who could do that one-to-one with him. Channel that passion into something productive!
I would make it that Xbox time can be earned by going to the sports/activities/doing his best at school. So it’s motivational rather than punishment for not going.
He’d have to keep going for a set period with sports/activities (I would say at least a month) and with a course see if through to the end. If he wasn’t enjoying a sport/activity, he could pick another one to try. It might take a few goes to find his thing.
Also give it a term to see if this helps him with school work, then get him a tutor to help him. It’s not a punishment, but helping him reach his potential.
I know it won’t be easy, particularly the initial transition period, but if you stick to it he should come through.