The Shenandoah’s are pretty much in my backyard and have been my go-to place to backpack when I have time. It’s a great place to go year round.
First, take whatever answers you get to your post with some common sense as the temperature and conditions vary greatly throughout the year and you need to pack for the conditions during your trip. Snow and rain are also a whole different ball game. It also depends on your behaviors too and how you choose to hike. For example, I’ve been quite comfortable in winter while on the move with a base layer of merino wool / SmartWool and merely a windshirt and Rab eVENT pants. However, as soon as I stopped moving, I got cold. So, you should be fine with what you mentioned while you’re on the move and you can regulate your head and hands with lightweight gloves and a hat (again, my suggestion is Merino / SmartWool. You’ll also quickly find that valley’s and summits are completely different in temperature and wind, so you’ll need to plan your stops accordingly. The difference can be about 5-20 degrees and a cutting wind or a quiet night. Picking your camp site is important too as if you put your Torsolite on a well used campsite you’ll get cold quick since there is no duff. Personally, I always seek out unused places which have a lot of pine needles or leaves as it helps quite a bit. Aside from the insulating factor, it is quite a bit more comfortable too and during the summer a pad isn't really even needed with the right site. A second pad may also be a smart choice as is common for winter hiking for some backpackers.
Based on your post, I wouldn’t say you’re a noob to lightweight backpacking as you have a lot of good gear, and let’s face it, we’re all here to learn something. Ryan Jordan’s book is excellent too and covers a wide range of topics that will no doubt help your search for information.
Others may differ in their opinion, but I’d swap out the Techwick stuff for Merino/SmartWool. To me, simply nothing regulates body temperature better and it doesn’t hold smell. Wool also holds about 80% of its heat retention when wet. If you want to forgo the need to bring two pairs of pants (hiking, rain), grab a pair made of eVENT. It breathes so well you can wear it even while exerting yourself regardless of the weather. I use a Western Mountaineering Carbou as a quilt after I couldn’t find something bigger (i.e. Nunatak, Jacks R Better, etc.) to go over my body (I’m 6’6” and 270), so our bags are very similar. You should be okay as long as you are layering your clothing system properly with your bag. You might want to consider a bivy like those they have at BPL as I’ve found that condensation will otherwise kill the loft and that’s what is keeping you warm. When I use a tent, I use a Six Moon Designs Lunar Duo which is similar to your Tarptent only a little longer. I wouldn’t use either in the snow, however. My snow option is a GoLite Shangri-La 2 which would likely work well for you and your girlfriend and they aren’t really that expensive. Depending on what you may encounter, you might want to find an option that can hold the weight of snow a little better as lightweight tents and those which are single wall (unless it is a Hilleberg) suffer quite a bit. The only other things I bring with me are the Cocoon jacket and pants sold on BPL which I use as part of my sleep system. Quite honestly the pants are a little too warm most of the time even in the snow. I have found that a second pair of socks is welcomed too as that’s about the only thing I feel like gets less than warm and lugging around a pair of down booties just seems like a bit much. Grab a nice fleece balaclava too as they work wonders. Getting one with Windstopper is the choice of some on this site. For rain and snow, just grab an inexpensive pair of DriDucks or FroggToggs and that should really cover you in the event that you aren’t wearing eVENT pants. DriDucks and FroggToggs breathe quite well. If you’ve got the money and you don’t mind the extra weight, go with eVENT….it’s great stuff and more durable. eVENT mitts are also great in the winter.
You didn't mention it, but get some hiking poles if you don't use them already. BPL and Gossamer Gear have some lightweight ones as does Komperdell, Leki and even your local REI. Ensuring proper footing in the snow is critical.
Lastly, if you’re in Shenandoah National Park, you likely won’t be able to start a fire. However, some places on Skyline Drive and off of the Blue Ridge will allow you to have one while on the trail. Having a fire is great in the woods, especially in winter. This might be a fact you'll want to consider when deciding where to test your skills for the first time as you could always fall back on a fire in a pinch in these locations.
Course, this is just what works for me and my experience. Others may have a different take. If you see a tall guy sporting the gear I mentioned on the trail, it might be me as I'll be headed that way several times in the coming weeks. Good luck.