Not the best treatment for a JM to be sure but I highly doubt it is doomed. These plants can be a lot more resilient than you'd expect.

As far as care now is concerned, I'd recommend planting in the ground over anything else. This is going to afford it the best chance of recovery. If this is NOT possible, you can pot it up using a very good quality potting soil (i.e. NOT Miracle Gro) but you don't want to keep it indoors for the winter. It needs a period of dormancy.

If you can, sink the container into the ground. If not, an unheated, attached garage or a very cool basement could work. Keep temperatures below 45F - right around 35-40F is ideal. Check periodically for water - it won't need much. Just keep the soil barely moist to the touch.

Not inside, no.
I pot mine in big pots with lots of room for them to potentially spread out. Then I bury the pot in the ground. I've done this with over 100 maples for about 6 years now. Slowly, after I can determine their sun tolerance, I put them actually in the ground.

If you must pot it for the winter, put it someplace where the pot won't freeze. No air underneath, nor too much water to freeze the roots. Up there, it only takes a few inches to protect it.

I never understand why people decide something is so fragile. I've dug up and moved peonies, all kinds of trees & shrubs, heuchera and hosta, and even have hellabores in unGodly full sun. Go figure.