Little update for those interested. We elected not to spend a full day in transit for TDP or the Cave of the Hands. I had a bit of a medical surprise while in El Chalten which called for attention and convalescence. We ended up doing Laguna Torre, Laguna Los Tres, and opted -- a bit too ambitiously in retrospect -- for the Viedma Pro glacier climbing clinic. Viedma Pro was pretty intense, we actually hiked across the glacier a mile past the intermediate groups and scaled 30-50-foot vertical ice walls with crampons, ropes, and ice axes. They taught us multiple climbing techniques, moved us through multiple levels of wall difficulty, and took us deep into sapphire-blue ice caves in the center of the glacier. We were able to keep up and got a lot out of it (my gf and I are both healthy, fit, late 30s) but not as much as people who'd done ice climbing or rock climbing before. My one complaint is we were on the glacier for like 5 hours without access to a bathroom, which is a bit too long not to specifically warn people about in advance. That's a long time to hold it in the middle of grueling physical exertion (and rappelling back down ice walls in a harness). V.Pro also included the ferry ride around the lake with up close glacier and ice floe views, great chance to relax and snap lots of photos. I think it was $250/person and worth every penny.
We had room 211, a cathedral-ceilinged corner room with a stunning view of the mountain range and valley, at Los Cerros in El Chalten. I think it was the best room in the house. The staff was lovely and very helpful, the room layout and facilities were quite nice (especially for a rustic lodge in a remote national park), and the breakfast was pretty solid. This is definitely the best hotel in El Chalten and at $300/night inclusive of taxes there's no point in looking at other properties in the area. The front desk can make any local tour arrangement you want and will drop it onto your bill. I'd read that Chalten is expensive but at the best hotel in town we drank limited-run bottles of wine which were 50% more in Ushuaia and Buenos Aires (identical bottle/vintage).
We ended up taking a private car from the Calafate airport to Chalten, Condor Taxi did it for $200 one way. On the way back, the vendor used by Los Cerros cost $300. The return trip driver told us some hilarious stories about driving one of those cross-border vans to TDP for many years and "not speaking English" (his English was excellent) during those 12-hour runs. The private car enabled us to stop at Estancia La Leona and and also slow or stop to view wild Guanacos and Rhea/Ostrich and horses and foxes on the open steppe -- a remarkably picturesque drive.
After our intimate communion with Viedma Glacier we decided not to do Perito Moreno and instead spent a leisurely half day at the bird sanctuary in Calafate. In Calafate we stayed at Posada Los Alamos, which has nice facilities but put us into a terrible room which was grossly misrepresented (they said it was a mistake), with paper thin walls through which we could hear the neighbor coughing all night. Overall Los Alamos was a pretty third-rate experience from bed to breakfast, wish I'd gone with another property in Calafate. They gave us a glorified single bed and tried to tell me that's called a queen in Argentina, then I realized they also called Kirchner a queen and I got the joke. Seriously, though, the room was like a dollhouse room, a real queen wouldn't have left any space to move around its edges. I strongly encourage looking elsewhere in Calafate, which has several luxury hotel options.
For anyone trying to decide between time in Calafate vs. Chalten, we spent 6 nights in Chalten and 2 in Calafate; if I had it to do over I'd have taken a night from Calafate and stayed longer in Chalten. Estepa restaurant in Chalten was also very good.
We ended up flying between FTE and USH, which was the right choice, thanks to feedback from this thread.
We had 5 nights in Ushuaia, where we spent 2 full days hiking in Tierra del Fuego national park (3rd day possible if you want to do Cerro Guanaco). The Fin del Mondo post office is cute, the Costera trail and the Hito XXIV trail shouldn't be missed. We also did the Pira Penguin tour, which was really cool in both senses (sunny day / freezing wind, and pretty unique fun). We got to see three kinds of penguins and some pretty dramatic scenes of predatory birds swooping in to hunt penguin babies during peak nesting; against the backdrop of Andean coast this felt like being swallowed up by a nature show in the best possible way. Weather was windy and rainy / freezing rain the first day or two, sunny and clear and warm another two days, and white-out snowing one day in the middle.
In Ushuaia we stayed at Arakur, which is a gorgeous hotel with exquisite facilities and some strange idiosyncrasies. Its grounds have trails and a nature preserve, where we saw wild-looking (but probably just loose) horses feeding and spying on us for a few km around the peat bog. Nice way to pass a few free hours. The restaurant, spa, and other services were superb. We had a senior suite, which was basically two connected rooms with two full bathrooms (each with a bath and picture window to enjoy the stunning Channel views), the second room had a living room setup instead of a bed. Highly recommend this property with a couple caveats about its weirdness: firstly, the front desk people speak perfect English but they're the only hotel staff who do. I have enough Spanish to get by but this can be tricky when you order the most expensive bottle of wine at the restaurant but can't ask for a decanter. Secondly, it seems that most locals opt for the dinner and grill buffet at the restaurant, which was fantastic if buffets are your thing but they're not really mine. This means the service at the restaurant is a bit lacking (e.g., unaccustomed to tips) if you elect to order from the regular menu. Breakfast buffet was the best we had on this trip. Because the suite involved two room numbers this created some confusion when signing a bill such that the restaurant called the second room's phone every day asking if we wanted them to hold breakfast for us (until I caught on and gave both room numbers). The hotel has an hourly minibus service to the town center and back up, as a tall person I found the seats unpleasant and the schedule erratic so we mostly used it to get into town and then taxis back up the hill (it's not walkable). The room had two stocked minibars, all soft drinks: at some point in the middle of the stay they started charging me exorbitant prices for bottled waters ($5/500ml), which struck me as arbitrary and tacky given my $600+/night rate for their best suite product.
Kaupe restaurant in the town of Ushuaia was excellent, fine dining on par with international standards. Otherwise I found the town center of Ushuaia forgettable, with throngs of docked cruise ship types drowning out its few charms.
Overall I'm glad I allocated an extra uncommitted day in each of Chalten and Ushuaia to account for errands (laundry, medical, misc supply runs, internet research when reliable) and the risk of weather related airline delays. Despite all the horror stories, we had a pretty positive experience on Aerolineas for domestic (business / prem economy) flights between EZE-FTE, FTE-USH, and USH-EZE. The only alternative, LAN, had fewer scheduled flights and no extra-legroom options.
Thanks to everyone here for the earlier input. It really helped me make the most of this trip in both relaxation and itinerary-maximizing senses.