Hi, everyone!

I've seen this topic posted about before, so I hope you'll forgive me for posting this! I have a few specific questions.

My mother in Indiana has found herself with a grey tree frog stowaway in her apartment; as they often do seem to, he probably hitched a ride in on a houseplant brought in for the winter.

It's now December and he's still kickin', though it's tough to say whether he's well fed at this point.

I'm a wildlife biologist, but not a herp specialist, so I've been checking with a few old friends and mentors on the best course of action, but I would love some input from folks who are personally familiar with tree frogs!

So, I've narrowed the options down to a few things that seem most practical and most likely to have a favorable outcome for our noisy friend:
1) Release him at the best time she can, best on weather, and transport him to a local park with woods, where she can place him under some leaf litter.

2) Prepare a terrarium for him.
3) Try to help ease him into hibernation somehow.

My concerns with option 1 are mostly with acclimatization. I know greys can survive freezing temperatures. But how quickly can they safely acclimatize? We've got rain today, with a temperature around the upper 30s. It'll be freezing tonight and in the 20s and 30s for highs the rest of the week. While I usually try to "let nature take its course," I'd feel guilty having my mom put him out to his doom after accidentally bringing him in. And she's a huge bleeding heart who is having a rough time lately and despite not being comfortable with the frog being loose, is feeling pretty invested in his wellbeing.

Concerns for option 2 are several. I don't think mom is interested in keeping him. I've read up on their care and feel fairly sure I could provide for him (so long as I can get my fiance to agree). I've heard some speculation that if you overwinter a frog and feed it, they become accustomed to being fed and are unlikely to fare well in the wild on their own anymore. What truth is there to this? I am not finding any formal data, but I'm skeptical, since frog hunting behaviors are pretty simple.

Another issue - I see on their care sheet that without the hibernation cycle, they are unlikely to breed. Well, that's pretty crappy for him if he doesn't get his hibernation cycle in. If it's too late to do so safely outdoors now, is there a method of helping him with that at this point, kind of late in the season? I might need some more specifics than the care sheet offers. Specific temperatures / time to acclimate to each would be beneficial. This idea might also be tricky since neither I nor my mother have a garage or anything.

I'd like to give this little guy the best shot at getting back in the wild healthy. The sooner we can get him back out where he belongs, the better, but if it would be risky to do so now.

So I guess my questions are:
* How fast can they acclimatize to temperature changes? (IE, how warm should it be (highs/lows?) before we attempt to put him out?)
* If I put him in a terrarium for the winter, do I ruin his reproductive chances? Would he at least be able to provide for himself?
* Is helping him get acclimatized and hibernate, either by keeping him or by acclimatizing him and returning him to the wild while he's "out" a reasonable option?
*Which of these options seems the most likely to give this guy his best chance at having a normal froggy life?

Thanks in advance for any help you guys can offer.