Needs help choosing a song for an audition?

I am a Show Tunes and Opera lover, I take vocal lessons, and hope to make it into the business, anywho in hopes of going to a good college I am doing a competition for scholarship money (and joining the military). It has three categories, vocal, instrumental, and guitar. To be honest with you I play guitar, piano, clarinet, and oboe, but vocal is my biggest love and pion so that's what I went with, currently my voice is not in the best place as of late, I am experiencing a lot of cracks going into my falsetto from my tessitura, lately my range has been limited, I can hit the highest a baritone can, and the lowest a tenor can, but lately no high notes!! Which is sad because I used to hit into some high baritone notes, and the countertenor notes, I had a very extensive range, I do my excercises, close to everyday, I drink a gallon of water a day, I always drink warm tea with honey after a half hour of warm up and an hour of excercises, I don't understand, my vocal coach doesn't understand either, it's making my song selection very small to choose from, as of now I have "Mellan Oss Tva" by Bhunter (not at all clical, but if I do all clical they will more than likely think I am odd, as I was told last year at this scholarship competition I went to last year in Atlanta) I was thinking of doing "Frisch zum Kampfe!" from Die Entfuhrung aus dem Serail" by W.A. Mozart, but I only sang that song amazingly five times out of practicing it ten, not precise enough!! I need a clical song, something that is in a foreign language, prefferably Deutsche or l'Italiano, cause those are the two languages I speak the best, and second being Svenska (Swedish) please help, also I purchased 28 Italian Songs and Arias G. Schirmer, and it's like either too high, or too low, mostly too high though.... how incorrigible.