Hi, I just got back from a few days on the AT in the Smokies myself. Temps were the warmest I've experienced since a 3-day trek in 1999. Daytime highs at 5000 ft were near 60 and nighttime lows were only down to the mid-30's. That being said, there was snow in patches as low a 2000 feet, left over from the storms of the previous week.
However, as for your gear list, you should be fine. Your clothing seem reasonable and you always have to option to pull up into your sleeping bag if it still seems too cold. You can also drape the opened bag around you like a shawl if need be while you're in camp.
Shelters will make life easier and as you're grunting up the 3000 ft ascent to Shuckstack you'll be glad if you save a bit of weight from carrying a full tent for a mere one night's useage. I actually prefer to carry a tarp and lightweight bivy sack. I use the Integral Designs Endurance bag cover, weighing about 11 ounces. In conjuction with the tarp, it is a very solid system that protects me from snow on the ground (it's big enough to put a pad inside the bivy along with you and your bag), as well as precipitation from above. My very roomy tarp and bivy (with stakes and lines) weigh under two pounds and I can tuck a partner under with me if I desire. If you want a solo pitch, you can find decent options in the 8 ounce or less range.
One note of caution would be to be prepared to alter your trip if 441 (Newfound Gap Road) is closed due to snow. It was when we headed out this past week. This would prevent you from staging your car at the end of the trek. You could still hike up from Fontana, then hike down to any number of spots on the Tennessee side, including Cades Cove, Great Smoky Mountains Institute at Tremont, Elkmont, or even into the areas very near Sugarlands Visitor Center. You would be surprised how easily you can make big miles downhill from Mt. Collins Shelter to Sugarlands.
Similarly, if you get your vehicle up to Newfound Gap, it is possible to get it snowed in up there for a couple of days or possibly more, so be sure to have some extra food and water available if you had to stay a bit longer than planned.