Method of Salaah

Q: How to attain khushoo and khudhoo permanently in salaah despite having doubts all the time? 

Q: In Ruku', instead of reading سبحان ربي العظيم, I read سبحان ربي الأعلى. Do I nees to make Qadha of the Salaah?

Q: Recently I learned to read the Quran and learned that a lot of the surahs I recite during salah (including Fatiha), I had been misprouncing. It was small mistakes like pronouncing س in places where there should be ص or ث. Was my salah valid even with these mistakes?

Q: 

1. If an Imaam recited an aayah of Surah Naba incorrectly in the fardh of Esha i.e. instead of reciting لاَ يَتَكَلَّمُونَ إلّٰا مَنْ أَذِنَ لَهُ الرَّحْمٰنُ, he recited لاَ يَتَكَلَّمُونَ مَنْ أَذِنَ لَهُ الرَّحْمٰنُ, will the salaah break?

2. If the salaah breaks, then if among the muqtadis there was a person who was a musaafir, should the musaafir muqtadi repeat four rakaats or two rakaats?

3. If the mistake was in Esha salaah and the Esha has to be repeated, then will a person who has performed witr after the esha salaah have to repeat the witr salaah as well? 

Q: Is it permissible to recite Surah Fatiha at the time of tashahhud if you don’t know what to say.

Q: I would like to know if I get the Imam in Ruku in Jamat, should I read Surah Fatiha first after takbir then go to Ruku or should I go to Ruku directly?

Q: If Surah Ikhlaas is mistakenly recited in the first Rakaat, what is the best Surah to then recite in the second Rakaat?

Q: In one musjid, the Imam Saheb read in the first rakaat of Fajr Salaah from the middle of Surah Tahreem,

يا أيها الذين آمنوا قوا أنفسكم و اهليكم

till the end of the Surah. Then in the second rakaat he read a different surah. Is there any reason for doing so? Would it not be better to start at the beginning of the Surah, read 2 pages, then in the second rakaat finish off the Surah?

Q: In fardh Salaat, is it appropriate to recite Ayatul Kursi in the first rakaat, and a Surah shorter than Ayatul Kursi in the second rakaat? For example, reciting Ayatul Kursi in the first rakaat, and either Surah Asr or Surah Ikhlaas in the second rakaat.

Q: If I am reading 4 rakaats Sunnah salaah and I read surah Naas in the first rakaat, what must be read in the remaining 3 rakaat?