Bob

Still dealing with the spider mites! It's been a long time.... sometimes you loose a few and it sounds like this one may have been weakened from being in bad shape for so long. Definitely keep the other 2 separated and to prevent the ineveitble mites we all seem to get in winter I'd go ahead and treat them with insecticidal soap just as a preventative measure and keep them in as high humidity environment as you can provide. I'm not the biggest misting fan but giving them a weekly shower seems to help if you can swing that. A simple inexpensive room humidifier has helped greatly for me but this is for a room stuffed full of plants so you'll have to decide whether its worth it for you.

Going back to the first don't freeze it outdoors , you'll just kill the plant. Keep it warm , humid(maybe a plastic bag over it for a while for humidity ) and keep using the soap. I only use store bought since it's usually safer than risking a dish soap that may be doing harm. Since it's so well rooted it may make it yet. Good luck with the plants and surgery.

Bob