1. I have no idea, since we went in August.
2. We went with the kids and most evenings we ate at restaurants we found while we were out and about, so my recommendations won't be helpful.
3. It seems there is quality shopping everywhere you go, so it's hard to advise. Though I didn't buy anything there, I enjoyed Printemps if for no other reason than it is kinda like visiting a historic department store, if that makes sense. There's another department store next to it that was more modern and had a wider range of stuff - that's where I got my jacket. You can easily hit them both in a few hours.
I don't know if it's cheaper now, but prepare yourself for sticker shock.
4. Things to do that aren't the usual:
Do have a picnic of bread, cheese, wine at the Eiffel Tower. (Bring a blanket because the lawn is kinda nasty). Plan your visit at sunset. Stick around at night and watch the light show every hour.
Also have another picnic on Pont Neuf. That was one of our favorite memories. Take one of the boat rides up the Seine first. We actually did this not once, but twice. Sunset is a nice time to do it.
(Bring along a backpack your hubby can carry, so you can carry stuff for a picnic - the best bread, cheese, wine isn't always near the best picnic spots.)
The catacombs!!! Not for the faint of heart, and you have to get there early because of the lines, but it's pretty cool if you're into that sort of thing. If you do this, there is also a cemetary near by which is worth a good hour or two of your time. If you like this sort of thing.
Take a ride on the Ferris wheel near the Louvre. Cheesy, but the view from the top is pretty good - and you can kiss at the top.
Sit in a sidewalk cafe every day, sipping coffee, tea or wine, around 4 pm, and people watch.
Take a hot air balloon ride. (Okay, we wanted to do this - the balloon was near our apartment at Parc Andre Citroën - but we never had the luck, because of the weather. If you are interested, you can check their web site every day to find out if they are going up).
If you go to Versailles, expect to blow a whole day and to walk a lot. My favorite part of it was Hameau de la Reine.
If you're into museums, the Louvre is amazing but I also enjoyed Musee D'Orsay.
There's also a big flea market on the weekend - can't remember what it's called or where it is, but we enjoyed that too.