It wouldn't work for me. I started getting cold in the Marmot Hydrogen and on the NeoAir (at separate times) when the temps got down to 40*F. By the time it got to 30* I had all my insulating clothing on and was still getting cold. At 18*F with a 20*F sleeping bag (WM Ultralight) and a 1/8" CCF pad on top of a NeoAir, wearing all my insulating clothing and a vapor barrier suit, I was nice and warm on top, but at the same time I was shivering underneath.
I basically had the same clothing you had except for fleece pants instead of Thermawrap. I also wore a balaclava and gloves, two pair of dry wool socks and wore my non-breathable rain gear as a vapor barrier between my midweight base layer and my outer insulation.
At a minimum, I'd get a much thicker CCF pad (maybe 3/8") or a NeoAir All Season or some other R5 pad if you're going below the mid-20's. The EN13537 tests for 20*F bags, I've read, assume a sleeping pad with an R-value of 5. You may need a warmer sleeping bag, too, but for starters definitely beef up the pad.
Admittedly, as a woman I get cold about 9 to 10 degrees F sooner than a warm-sleeping man, according to EN13537 ratings and my own experience.