Hi there! I had a couple of Grays turn up indoors in February, one adult and one nearly an adult. I used the activity of my local wild population as my cue to release them. When I could hear the wild ones chorusing on a nightly bases, I set them free.
They are built to survive freeze/thaw cycles in the spring, and from what I've been reading they don't seem to need to ease into a cold period. However, as long as you're willing to keep feeding them, if you want to hold on to them until it's a little warmer at night it shouldn't hurt them.
It's too bad about the missing legs, those little ones will probably have less of a chance on their own. You've given them a much better chance than they would otherwise have had though.![]()