October 8 day Paris itinerary

Since you've included some museums, you might consider Musée de Cluny while in the Latin Quarter - medieval art and artifacts.

https://www.musee-moyenage.fr/en/

I, personally, would have a hard time spending an entire day near the Eiffel Tower. Some attractive vistas from Trocadero, but I've never felt the hike from Trocadero to Champs de Mars was much more than a long walk. (maybe because the last time I did this, it was a very hot summer day!) Have you considered Les Invalides - Napoleon's Tomb and the Army Museum in the area? Napoleon's Tomb is unique and the museum is quite good - the very taxis that drove the troops to the front in WWI as well as Napoleon and WWII. Another museum in the area - Musée du Quai Branly - indigenous art and artifacts from various world regions.

taurus0515,
Your days sound pretty well-planned, grouping things by area, in general. Your Wednesday in Le Marais (note spelling) seems a bit crowded. Be sure to allow yourself enough time to enjoy the Carnavalet, and enough time in the Pompidou. You don't want to be rushing through places, and rushing from place to place. Be sure to factor in enough time to enjoy a nice lunch on all your days, or a sit-down at a cafe to people-watch. On Thursday, give yourself plenty of time at the Musee d'Orsay. It's a real gem. And I would allow an hour at Sainte Chapelle. Factor in time to walk from sight to sight. You can't really walk fast in Paris. Even if you could, you would lose the ambiance of the city.
Going from the Tuileries Gardens, through the Place de la Concorde, up the Champs Elysees is a long walk. From the Place de la Concorde to the Arc de Triomphe is an uphill walk (not a steep grade, but probably a good mile or more in length). Allow yourself enough time. Maybe it would be better to start at the Arc de Triomphe and end at the Palais Royale.
On your Sunday late start, be sure to allow a good hour at the Rodin Museum (I usually spend two hours there, even though I go every time I am in Paris...it's a favorite of mine). Another full hour at the Invalides (Napoleon's Tomb, lots of suits of armor!) Add in walking time from there across the river...it's more than a block or two.)
The Eiffel Tower area is not far from the Invalides, Rodin Museum and Pont Alexandre III, so you can rearrange these things within those two days if you don't get to everything as planned. (We have viewed the Eiffel Tower from the area around it, gone to and visited the Invalides, and then the Musee Rodin, lunch at the cafe there, following up with a walk to the bridge.)
To reiterate, factor in time getting from place to place, allow some down time for a comfortable lunch and maybe a stop for an aperitif and some people watching, and soaking up the "air" of Paris!
Have a wonderful time! Amusez-vous bien!

Here are my thoughts:

Oct 11: Looks good. If you are concerned about jet lag you might look at the app called TimeShifter. It helps you recalibrate your circadian rhythm by staying out of the sun or wearing sunglasses at particular times. The first Round Trip is free. I had no jet lag last time I used it last summer.

12: If you do have jet lag you may be up very early instead of sleeping in, then may need a rest in the afternoon. Otherwise this looks fine.

13: Ok. Im not a shopper so others will tell you if Galleries Lafayette will work in this time frame. If you buy stuff will you return to your hotel or carry it with you?

14: This day looks light. I avoid the Bir-Hakim Metro area because I have always had the impression this was a big pickpocket area. I may be wrong. Just make sure you are pickpocket proof? Are you interested in Art Nouveau? There are some cool facades a block or two East of the ET in the Avenue Rapp area.

15: Fine

16: You might consider one of the walking tours of the Marais from Paris Walks if they offer one on a day that works for you. www.paris-walks.com

17: This looks fine. Will you want to visit Sainte-Chapelle? Notre Dame will be a walk-by. The Deportation Memorial is at the end of Ile de la Cite, east of Notre Dame if that is of interest.

18: looks fine. Luxembourg Palace is where the French Senate meets and I don’t think it’s open to visitors. The Musee du Luxembourg and the Gardens are open.

19: The gardens of the Palais Royale are nice but I think there are mainly offices in the building so not really visited. If you were interested you could visit The Orangerie Museum which is at the Place de la Concorde end of the Tuileries. It’s got Monet’s huge water lily canvases.

You’ve done a good job of grouping things together.

taurus0515,
ORDtraveler mentions the Cluny museum. I concur that it is a real treat. I went there for the first time last year and was blown away by the medieval art and antiquities. Your Friday would be a good day to fit that in. It is a good 2-3 hour visit (I confess I spent four there!). It is not too far from Luxembourg Gardens. It fits well with your Latin Quarter day. When you speak of the Luxembourg Palace, do you mean the palace building? It is a government building where the Senate meets. Perhaps you are thinking of the Luxembourg Gardens, an often-recommended place to go in Paris. Forgive me if I am wrong, but the gardens offer a lot more "Paris" than the palace.
Again, have a wonderful trip!

taurus0515,
A few more thoughts. Montmartre area is on a steep hill. Just factor that in when you decide on your metro ride there, or a taxi there.

The metro stop there is deep underground. There is an escalator, but sometimes it doesn't work. (I am 80 y/o, so I will opt for a taxi next time I go there.) It is often pooh-poohed, but the Basilica of Sacre-Coeure is lovely inside, with magnificent mosaics (early 20th century). I am glad that I have visited it!
Re your Seine cruise. We have never chosen a cruise with dinner. Vedettes de Pont-neuf are our favorites. The leave from the tip of the Ile de la Cite, have a good narration and are inexpensive. Get in line about 45 minutes early to get a seat up top. (Bring a jacket!)
This is not a dinner cruise, but we like it. You can order your tickets online ahead of time, but in Sept. you may be able to walk up. You would have to check that out. If you want to pick up your cruise near the Eiffel Tower, I believe you may need to use another company.
I am glad to see you will visit the Opera Garnier. It is often neglected by many US tourists, but it is beautiful. And the Galeries Lafayette are not just for shopping. The inside with the dome is a treat to see. Lunch there? A cafe on the 8th floor would be a fun experience, but I don't know if it is overpriced.
Mine this forum in the search box to get input from the forum members. Just search for whatever sight or activity you are curious about. I have learned so much here from others' experiences when planning my trips.

Thanks all. I have made a few edits based on your feedback. Eiffel Tower day is just a placeholder for now. All depends on the time of the tickets. Will try to get tickets for evening. If can do that, will re-arrange the day to get enough rest during the day and be in the ET area until we can see the sparkling lights from upclose or from the Trocadero place.

You should consider a food tour. The one we did a few years ago with Secret Food Tours was great. If you like classical music, you should consider booking a classical music concert in the late afternoon at Sainte Chapelle.

We are Vegetarians. So, the food tours may not be interesting. Also, I do not see any Concerts in The Holy Chapel in October.

The Arc de Triomphe does have an elevator for those with limited mobility.

Enjoy your trip.