Questions about my itinerary - TDP + El Calafate + El Chalten

My girlfriend and I are going in late September/early October, and we have some questions about our itinerary. For each destination, we're trying to prioritize the best attractions on the sunniest days, so we're flexible and can change the order of activities within TDP, El Calafate, or El Chaltén.

DAY 1 (Puerto Natales): Santiago → Punta Arenas → Puerto Natales + explore the city
DAY 2 (Puerto Natales): Mirador Base Torres
DAY 3 (Puerto Natales): Grey Glacier and Grey Lake
DAY 4 (Puerto Natales → El Calafate): Explore the city
DAY 5 (El Calafate): Perito Moreno Glacier
DAY 6 (El Calafate): Todo Glaciares (boat trip to Upsala and Spegazzini)
DAY 7 (El Calafate → El Chaltén): Mirador de los Cóndores, Mirador Las Águilas, and Chorrillo del Salto
DAY 8 (El Chaltén): Laguna de los Tres
DAY 9 (El Chaltén): Laguna Torre
DAY 10 (El Chaltén): Loma del Pliegue Tumbado or Piedras Blancas Glacier
DAY 11 (El Chaltén → El Calafate): Return to Buenos Aires

If we were to rent a car in only one place, where would you recommend doing it? In Puerto Natales, I think it would help us get to the Base Torres trailhead earlier and return to Puerto Natales without any issues. Is there any downside or risk to relying solely on the bus? In El Calafate, I could rent a car on the last day to drive to El Chaltén and enjoy the scenery, but it would probably sit unused until we need to return.

How reliable are the buses from El Chaltén to El Calafate? On our last day, we're planning to catch a flight around 1 PM.

Are we spending too much time in TDP or El Chaltén? I couldn't find many other activities in El Calafate that seemed worth adding, but I'm worried I might be missing something.

As for the hikes, are we being overly ambitious (for the amount of long hikes), or is this itinerary reasonable for a normally fit couple?

Appreciate any advice!