Many years ago I was a wildlife rehabilitator, specializing in critters like skunks and raccoons, and often any other small mammal or bird that got injured. Loved the work, although getting skunk-sprayed at close range was pretty awful.
One night I saw a mother opossum who had been hit by a car, so I stopped to pull her off the road, and realized immediately:
1. She was dead.
2. She had a pouch full of baby possums.
The babies were the size of a peanut shell, hairless, blind, totally helpless. What to do?
I took them home, set them up in a tissue box, got an eyedropper and some warm milk, and tried raising them.
After a few weeks, and transfers to successively larger boxes, they looked and acted exactly like this:
I released them to the wild with a prayer.
Everything you wrote about them above is true. I would only add, it's the adults that act like that. The young'uns can be pretty cute. Teeth are sharp as hell, though. Ouch!
When my daughter Elen, now L/CPL Elen, USMC, was volunteering for a wildlife rescue, she took a class on caring for infant wildlife. One of the lessons was about rescuing the babies from dead mother opossums and rearing them.