There's nothing that can be done to fix an echo IMO that is captured by room mics, and there is also not much that can be done with respect to proximate shrieking.
If the shrieking is louder than the loudest peaks of the music, you could try a little compression, or a limiter, in post; all that would do, however, is reduce it a little bit relative to the rest of the music. Screaming/shrieking from a human voice crosses over too many frequencies also corresponding to the instruments, so you cannot really EQ it without also negatively affecting everything else.