Max also has severe problems with large PNGs.
Since ILM released the OpenEXR specs many years ago, we haven’t used anything else for output.
As for the emission, I would suspect the FumeFX Birth has an issue. I have seen this back in 2007 when we first tried to use FumeFX particles + Krakatoa on “Journey To The Center Of The Earth 3D”, not sure what the problem is but it is quite obviously not on our side. You should really talk to Sitni Sati about it, there might be something they know and we don’t.