Excuse me. Why are you worried about repotting? Leave well enought alone. If you have to ok but better to wait till spring. I believe all plants like a quick draining mix. Like the kind for cactus. Your plant looks great. Never saw one like it befor. I would like to find out more about your plant also. I never have room in my house at winter time. That's why I would wait till spring when you can bring it outdoors. After the shock of transplanting, it may need warm humid surrondings?? Let us know how you make out on this.
Stush.
