I have never smelled the byproducts of a possum so I cannot comment on the developer.
The blix is just about odorless and takes on more of an ammonia odor as you process. Use of a stop, or addition of 28% acetic acid to get to a pH of about 6 - 6.5 will remove the odor. I use a stop. It gives more even results all around.
You can process from 68F to 100F with no problems by adjusting time. There is a tiny color balance shift on the magenta yellow axis with Endura.