The app is very incomplete for Spain because Spanish railways don't share their data with the rest of the world.

Do you have a specific date in mind? That makes it easier to come up with suggestions.

Is this the only journey you'll be making? A pass might not be worth it just for this journey.

As rian tells-for only this trip a pass is not worth it, but maybe you plan also other trips in the time. Note that it allows only 2 days of use in your own country, DE.

The best nighttrain and in fact likely only one for you is likely the Cerbere (=FR border stop just north of ESpana) to Paris,

Then add any train (the faster, the higher the supplmt VLC-Barcelona and a very local Rodalies along coast to Cerbere (very, very hard to find timings, very much hidden somewhere in renfe.com. Renfe must be used for all times in ES, from Cerbere the trusted bahn.de, but cut it up in segments.

You need passday 2 for to cover Par->B via whatever route-the direct overtheborder TGV and even more Thalys to K cost a very high supplmt. on a pass.

This SNCF overnight only has seats and couchette=liegewagen, NO real sleepers (the fancy of many) and as for now goes 3/week, expected to be daily in summer.

Thank you both! My wife ended up deciding with the distance we would just bite the bullet and get a plane ticket. Thank you for your answers!