He has a continual flow of prostatic fluid, without feeling any desire

This is considered to be a continual breaking of wudu, like incontinence of urine, so he has to do wudu before every prayer, because this is something which breaks wudu as it is something which comes out of the front or back passage. If something comes out whilst he is praying, he does not need to repeat his prayer, or stop praying, because it happened involuntarily, and it does not make his clothes impure (naajis) whilst he is praying. However, after the prayer he has to do wudu for the next prayer if something comes out after the first prayer, and he has to clean his clothes for the next prayer. He should try to wear a pad to absorb what comes out, so that it does not contaminate his clothes. (He can pray in jamaa’ah as a member of the congregation, but he should not lead the prayers when he is in this state, because his tahaarah or purity is incomplete). He should also try to get treatment for this. And Allah knows best.