Spending Sunday afternoon to Thursday early evening in Paris-what should we do?

Here are our host's sightseeing recommendations, and a lot else, for Paris. Your timetable would let you visit all the places you mentioned and more. In planning, note that many museums are closed Mondays and others Tuesdays. Consider buying a Paris Museum Pass, which could save you money and certainly will save you time by letting you skip ticket-buying lines.

I'd recommend a Seine cruise, daytime and/or evening, but not a dinner cruise. You don't want to be looking at your plate when you could be looking at bridges and monuments and people. You don't need to reserve for a regular cruise so you can do it when the weather's right and you want to sit down for awhile.

The Louvre is a wonderful and vast museum, you could spend a whole day and not "see everything." Focus on the items or periods that interest you most. I believe it's open Wednesday evenings, with smaller crowds, if that helps your planning.

Does "Monet" mean his paintings at the Musee d/Orsay, the Orangerie, and/or the Marmottan Museum? Or his garden and museum at Giverny, a day trip out of the city? All would be good choices but you may want to choose one or two unless you're a very big Monet fan.

I would like to advocate to not try and schedule every minute of the day. Jet lag, weather, sore feet, museum overload can all affect how long something takes or whether you can tolerate 'another church'.
I suggest you sit down and list what you think you want to see, then check what is open on Mondays. Check the Museum Pass options as to whether it is worth it for quicker entry. Then I group my list geographically. I tend to out my priority meuseum first on a day list and queue a little early for it rather than decide weeks in advance that I will go at xx a.m. on xx date and buy a timed ticket.
Having a guide book with you means being able to add sites if you find you have done your main list in a short period of time. Or use the spare time for a leisurely lunch, glass of wine and people watching.

Your days of visiting match fairly well with the Navigo Decouverte Pass.
This can save you some money and is pretty convenient.

https://parisbytrain.com/paris-train-metro-week-pass-navigo-decouverte/

Seriously, identify about a dozen things you would like to do and then do half of them. Anthony Bordain's advice for Paris is to plan as little as possible.