from Sarlat to Paris

You can drive it in a day. Probably quicker than you could make all your air connections if you were to fly (from Bordeaux or Toulouse, I presume). Another reasonable option would be to take the trainfrom Brive, or the TGV from Angouleme. I don't any of those options is inherently better or worse than the others, it's up to you.

It will take awhile to get from La Roque east to the autoroute, so get an early start, but very scenic. You can get onto the A20 after Souillac, but you can save some toll (peage) by taking the D820 north, just after Souillac, and paralleling the A20 to the interchange just past Nespoulis (easier to see on a map than to describe). But overall an easy day's drive to Paris, much more interesting than flying. Of course you should try to ditch the car (not literally!) as soon as you get to Paris, it will just be a nuisance there.

It takes a while to wind your way back to the Autoroute. Once there, you can make Paris in a day easily. It's a lot of driving, so I'm afraid that eating along the way means the Autogrille. Suggest dropping your car at Orly Airport and going into Paris from there by bus.

Why not take the train? It's not too far a drive to Brive-la-Gaillarde where you can leave the car and take the TGV to Paris. It's just a bit over 4 hours train ride and you can relax and enjoy the scenery.

You can drive it in six hours including a couple of quick stops.

Sarlat is a great visit. Don't miss the tank museum. It is a reasonable drive back to Paris, although we did not make the entire drive non-stop.