You are a good sister. It is tough when someone we love is hurting themselves. Getting people to change is hard. Here are some thoughts, many of them from posts here in MDA.
Diet is the most important part of primal. So if you got him to change that, it would help a lot. Many folks here do distance events. Mark, a former champion marathoner and triathlete, would say if that's your passion, do it, but yes, you are damaging your body.