Spokes flex during a ride. They flex more the heavier the rider so breaking in the middle is the weak point of that particular spoke. It may be that the rim itself is ok and has "warped" because the spoke broke and there are not a lot of spokes to share the load so the rim may warp more than a wheel with more spokes. You can get the wheel rebuilt with a heavier gauge spoke and that may, or may not, work out. Your weight is the culprit.
You could also go the route of a 36 spoke wheel...you could use a heavier duty rim with heavy gauge spokes and get a stronger wheel. You should be able to find a built wheel with the needed sturdiness but perhaps you will have to go the custom build. At least you can specify the hub, rim and spokes that will suit your needs.
Good luck and keep us informed.