Mistakes in Qiraat

Q: I read Suratul Kawthar reading the letter "th" with a letter "sin" does that break salaah? I read in a fatwa that it does, true or wrong?

Q: In my 'Asr Salaah I recited a verse of Surah Faatihah and whilst reciting I thought I made a mistake, and thought I'd repeat that verse and I didn't
stop reciting until I finished the verse, and then I recited again, but during the verse in which I thought I made a mistake, I was like “Shouldn't I stop?" But I carried on until finishing that verse; now I wonder, does this count as a purpose addition in prayer by finishing the verse in which I thought to have made a mistake? And is my Salaah valid?

Q: First rakat of ishaa I said 'Ar-Rahman Ar-Raheem' but then I don't know whether I said the ha or HA with 'Ar-Raheeem'. I chose to ignore it as a doubt. During Salah I made many mistakes and corrections in the essential aspects - then after completing the prayer [all four rakaats] I ended prayer and did two sujood uh sahw. I went downstairs to get a drink, came back up then I still had the niggling doubt about whether I said ha or HA in 'Ar-Raheem' so I thought like you know it hasn't been a long time since I made Salaam so I said takbir and performed 1 rakaat in replacement of the rakaat in which I doubted with the full tashahhud and exited prayer and did two prostrations of forgetfulness Now plz tell me is my prayer valid or not?

Q: My local imam makes some mistakes sometimes in salaah and I need to know whether these mistakes invalidate the prayer.

Mistake 1) The imam sometimes says hamza/alif Instead of saying ein for reciting quran, does this invalidate the prayer?

Mistake 2) For the name of Allah, Al-Quddus in the quran, the imam changes the seen into a saad-does this invalidate the prayer?

Q: If in "Ihdeenas-Siratal-Mustaqeem", I recited dee with a daad mistakenly instead of daal does this invalidate the namaz? I don't know for sure if I done it, but it seems likely so should I repeat the namaz or is it an acceptable mistake? I didn't repeat it afterwards.

Q: I read a book called Umdat ul Islam written by Abdulaziz bin Hamidullah in Persian some 700 years ago that if one reads the word hamida of sami Allahu liman hamidah with the letter ه instead of ح the salaah becomes faasid. Is this correct, it was also written that if you read Allahumma salli, the word salli with a س and not a ص the salaah is faasid. 

The book in question is it a authorative book? It says also some strange things like that in Jami al Fatawa it is said that if a person makes zina with a animal the animal should be killed and burned, and the person should also burned or a wall should thrown on him.

Q: According to the book Halabi Kabir p. 480: 

Is the invalidity of salaah lifted when a mistake that would invalidate the salaah, is re-read correctly?

Q: I read in a book that if you change a letter during recitation in salaah, the salaah is broken. Such as reading the letter ت instead of  د such as at the end of Surah al Falaq reading HASET instead of HASED. But somehow when I recite HASED no matter how much I pay attention to recite it with D I hear a T sound at the end coming out. Does this still break salaah? To break salaah does it need to change meaning, if HASED is read as HASET does it change meaning?