Mmh. Very nice, tricky question : with three pieces on the menu, and two given pieces on spot 1 and 3, two very extreme pieces in evironment and mood, what is left, the gap, number two, is more than just a center here. I imagine myself, after the final movement of the Opus 35, standing on shaking legs under the dark galaxy in a nebulous graveyard feeling the cold wind around my ankles. And now, number two is the question but... with number "three-four" I'm lying on my back, surrounded by pink and violet flowers and looking kind of carelessly at the clouds, is this the garden of Eden ?, with a possibility of joy in the air.
For me too, my mind was drifting by Janacek for number two ; the 7 to 8 minutes of "In the Mists" - it is not the 'schwarz' of the Chopin and it keeps some distance from the flowers and the delicious milkfoam of the Debussy ; "In the Mists" is well, still somewhat in the mist, but there are some colours trespassing the dark grey landscape.
Another number two (very subjective) would be BWV 849. The praeludium has this very vapoury quality to me, it can bring and keep me in some kind of dreamy state, it has a very hypnotic quality. The fugue is extremely gripping, almost unforgiven, but altogether there is finally, after the draconic opus 35, some seriousness that could create an illusion of relief. It could be a nice transition from the dark, cold night of the Chopin to the more compassionate evening of the Debussy. This Bach as 'in between' - why choose for balance or equilibrum ? - I think the program in its entirety with your two given choices, has a lot of potential to become an overwhelming, flabbergasting, mindblowing experience. I wish you anyhow the best if your question is 'for real', I hope you will survive the recital

and nice question anyway.
Kind greetings