Square pattern and stair-steping issue in Simulation

[turner_studios]

My time scale is set to 1. I'm attaching the file which was done in Maya 2014. Also is there a way to get more detail in the fire area? The smoke looks great but the fire looks a bit voxelly. I also tried to make a version where it explodes fast and then have the smoke as I have it now but when I animate the time scale, the smoke looses it's billowing quality and it's super dispersed.

Also when I rendered the sequence, the multiple scattering seems to be flickering, not sure what's causing that. It was rendered locally, not on a render farm. Here's the link to the video.

https://www.youtube.com/watch?v=MLFt-4dQ...e=youtu.be

Thanks for your help in advance.