What is "my level"? (absence of public performance)

[aklvkk]

There's a college piano audition coming up for lessons (auditioning to get lessons) around early September. Needless to say, I've been practicing a bit. However, I'm starting to have doubts about my repertoire. It's supposed to be a short interview-audition and I'm supposed to prepare 2 pieces. I've been practicing Rachmaninoff's Etude Op. 39 No. 6 and Debussy's prelude Feux d'Artifice.

I'm worried about my choices now. (I know, perfect timing  )

I haven't played in public for a few years because I quit piano lessons for financial reasons. When I did play in school performances, it's been my own compositions that I could quickly improvise on when I make a mistake. As a result, I don't know what kind of "level" I am on, and I don't know if I should just change the above to easier selections. I practiced Chopin's Ballade No. 1 and 4, his etudes from op. 10 (1, 3, 4, 12), op. 25 (1, 6, 8, 11, 12), Liszt's B-minor sonata, Beethoven's Appassionata, etc. But... I haven't really brought them up to a "concert-level" performance, especially considering I've been practicing on my ancient upright only. I manage to hit the notes on tempo with what I think are acceptable interpretations but that's about it.

Also, no, I can't perform my own pieces (I emailed the chair of the department).
It has to be a short audition and the chair said they'll most likely cut me off because of time constraints anyway.

I'll post videos of my performance of the two pieces later but I'm worried I'll botch up the real one because 1) I haven't played a live performance for so long and 2) it'll be on a grand piano. And I'm having a crisis right now because all the practice I put in both in school and out seems to be meaningless if I can't even perform properly in public.

I have a week to practice once I get there, and I'll be able to practice on a grand by then because the campus has a lot of accessible Steinways.

DOES ANYONE HAVE ANY SUGGESTIONS, PERFORMANCE AND REPERTOIRE-WISE? Like are there any other short pieces that are somewhat technically demanding overall but not necessarily as difficult as the ones mentioned above?