Paris in 3 days

3 nights is only 2 full days, unless you are coming from somewhere really close.
But if the three days you list are full days indeed, they work. You just have to be OK with missing many highlights of Paris.

I would just start with Orsay on the first day, because museums close earlier than the Eiffel Tower.
And don't bother with Shakespeare and co, it is just a used bookstore which somehow has a line to get in. Also, it is literally opposite Notre Dame (which can only be seen from outside, at a distance), so if you are already going to that area the previous day, you can have a look.

how does this compare with Rick's suggested itineraries? Or those from Fodors and Frommers?

Also note that various museums close on various days, and some are option on certain nights, Rick has a list of those as well.

As far as ambition, those sound like full but flexible days. Much of what you’re getting into can be fairly short or several hours and it sounds fun!

Sounds like a lovely few days in Paris. I would stop by Ste. Chapelle on day 2.

Thank you all! I feel much better about our itinerary.

The secret of a short time in a place where one could spend weeks is to prioritize what is important to you. It looks like you have done so. Also, when you are actually there, you can adjust if you find it is too much and edit a bit more.