Japanese Red Flowering Quince Bonsai Questions

I recently ordered a 3-4 year old quince from Brussel's in Mississippi. I am in Indiana where temps are now 20-40 degrees F on average, and likely will be for the rest of the winter.

I have the quince in my east facing sun room, out of the wind and snow and cold but still stays ~32 degrees F. It gets some direct and indirect sun in the morning and indirect light/shade past noon. It has been dipping closer to 15-20 degrees lately F so I figured I'd leave it in the sun room until warmer weather hits. Is this the best option for giving it a quick dormant period until Spring? I know dormancy should be 2-3 months but it just came in from the nursery in Mississippi.

How fast do they go dormant typically? What are the signs of dormancy? Any thing to do to help it come out of dormancy? It came with a few flowers and has more about to pop. Will it drop leaves/flowers or both?

Thanks all!

Dormancy is quite complex process.   Right now your quince is in the stage of post dormancy  I believe ie ready to go but waiting for the higher temps.  It is still frost hardy during this period. Flower buds and leaves develops quite early.  All my fl.quince have nicely developed flower buds, some have tiny leaves as soon as from early Feb with temps at nigths -7°C.  

Re your question: I would keep the plant at +/- 32°F.  If the temps are higher during the day - take it out and get it back in case of frosty nights.