Method of Salaah

Reciting a portion of one surah in the first rakaat and reciting a portion of another Surah in the second rakaat

Q: If a person recites from the middle of one surah in one rakaat and from the middle of another surah in the second rakaat or if a person recites from the end of one surah in one rakaat and from the end of another surah in the second rakaat of a fardh Salaah, will the Salaah be valid?

Incorrect pronunciation in tashahhud

Q: I have one major problem during salaah and that is that I cannot pronounce in the tahiyyaat the last letter (n) of the word " as saliheen" especially during the first tashahhud. So I keep repeating it, until I manage to pronounce it. If I will recite it as "as salihee" without the last letter "n" would that be also valid and the meaning still correct? Or should I recite like "as salih" without "een" at the end, like the tanween we do not recite at end of ayaats?