Overwintering a sulking Dwarf Korean Lilac

This spring I repotted a dwarf Korean Lilac for my wife. It has been in a nursery pot for two years and had tolerated the rather cold winters we have. Lacking any definite repotting information I assumed it would be best to repot before the leaf buds opened. I took care to disturb the roots as little as possible, and only a couple needed any trimming. A few leaf buds subsequently opened, but the rest seemed to be arrested in their development. Overall, the bark looks healthy and not shriveled and dried out as with a branch that has died back.

Now it is autumn, and I am wondering what is the most advisable course of action for winter? Previously, I set this plant along with my other bonsai/prebonsai on plywood on the ground and mulched around the pots with leaves. In its apparently weakened state is that a good course of action? I could winter it in a more sheltered location, or even in a cold part of my house. I am making an assumption that even if it is sulking it needs winter dormancy, otherwise I would consider putting it in a ICU situation as my climate tends towards low humidity.

Some of mine are outside and loosing their leaves, preparring for the big sleep. I have 3 others I that were started as cuttings this year. THey are in the basement under lights and kept between 65 and 75.
I would recommend over wintering it in an area that can get cold enough and out of the wind, but not letting the roots freeze. I only water when the weather will allow for good drainage before it would freeze again.

Dwarf Korean lilac, Syringa meyeri, should be fully hardy in your climate. Plant it in the ground to recover.
Iris