The photo is not in good light so it is hard to make out details. The fact that the plant is wilting is telling me that you are not watering enough and probably not deeply enough. If the pot has a drain hole, soak the pot in a bucket of water until the bubbles stop to make sure that the entire rootball gets evenly wet. When you water you should really water so that salts are flushed from the pots and all of the rootball gets evenly moist. Most shrubs and trees do better if they can be outside when the weather is warm. Leaves will start dropping if it does not get enough light. If you can gradually harden off the plant to the outside. Start with an hour in the early morning and gradually increase the time outdoors until it is acclimated.
I would not repot until the plant is fully acclimated. Wait a few months for that.
I don't usually like to try to make a bonsai out of a plant with large leaves. I would make topiary instead.