Regretfully, this is not an easy thing to deal with on a technical level even in editing, during a live performance I'd say he has got to learn how to perform properly. This is a performance issue, and can't really be treated at all on the fly. Had it been heavy esses, then at least you could had tried de-esser on an insane setting, but P's are in a wide area shared by lots of other vital sounds in voices.
You could use a limiter though. It's not ideal for things like live performances, but if you can't replace him, then you will not have much choice. Is he aware of his flaws? I don't know if you're the director or the soundie, but if you're the director, then you must make him deal with this and train that away, if you are just the soundie, make the director aware of the problem and do your best with the limiter. It will probably not sound good, but at least it will not blow the speakers...and ears....
The breathing though, there is absolutely nothing to do about. For you.