Recommendations for Le Marais

I'll address item 1) : check out la Cafeotheque, it's not super close to you but still near the Marais, right along the Seine. Great coffee place with many different preparation techniques and varieties.

You're just a half km from Jacques Genin, so that's a relief. Trendy boutiques all over the Marais.

On the weekends a big part of the Marais is closed to vehicles and becomes a huge pedestrian mall, lots of locals as well as tourists.

Appreciate the information thus far.

Coffee Spots
Le Peloton Cafe
Yellow Tucan
Fringe
Cafe Pinson
Neighbors

the Marais is also a great area for boutique fashions, your wife should enjoy shopping there.
The Grand Magasins (Bon Marche, Galleries Lafayette, Printemps) and BHV are also great if you want to go a bit more upscale.

For high-end fashion, your wife really needs to visit Avenue Montaigne in the 8th and Rue Saint Honore in the 1st. Most of the big designer shops (Channel, Prada, etc.) are on these two streets. They maybe way out of your budget, but it is a memorable experience to stroll along and window shop.

From the little I've seen, the small boutiques in the Marais are the best.

Check out these Paris foodie blogs:

ParisByMouth
David Leibovitz
Chocolate & Zucchini

Merci, a "concept" store at the edge of the Marais, 111 Blvd. Beaumarchais might merit a look.

https://www.merci-merci.com/en/

In 2009 we ate here twice. I see on TripAdvisor that the place is still going strong and highly recommended. I remember the owners were so very friendly and they opened early (6:30pm) I think.
the food was delicious. I fondly remember the rack of lamb on mashed potatoes...sigh. They also offer a 3 course fixed price menu. I hope you try it.

https://www.tripadvisor.com/Restaurant_Review-g187147-d1335980-Reviews-Les_Bougresses-Paris_Ile_de_France.html

We have had 2 wonderful meals at l’Ange 20 at 44 rue des Tournelles close to Place des Voges. Check out their menu on line which is very affordable, and everything is delicious. Do make a reservation as the place is quite small but very friendly.

I hear good things about Back in Black cafe for coffee - less than a 5 minute walk east of Place des Vosges.

Not in Le Marais, but we plan on going to Canards et Champagne when we are in Paris. Duck and Champagne...pretty much the only things on the menu!

I am commenting so I can follow this post as well. We are looking for fun places, and your tastes sound similar to ours. We are starting our trip with 2 days in Reims as well.