Social distancing in salaah

Q: Is social distancing in salaah permissible? My ustadhs say its not permissible and its makrooh tahreemi and that's what I follow but at home, my brother says its allowed because the hadith needs interpretations and that Hazrat Muhammed (sallallahu alaihi wasallam) said that flee from a leper. So how would you flee from a lion? He also said that Umar (radiyallahu anhu) didn't want to enter a land of the plague and he said that all the Ulama that say social distancing is not permissible are weak in usoolul fiqh and weak Ulama.

The masnoon dua of iftaar

Q: When should the following masnoon dua of iftaar be recited. Should it be read before one opens his fast or after one opens his fast?

اللَّهُمَّ لَكَ صُمْتُ وَعَلَى رِزْقِكَ أَفْطَرْتُ فَتَقَبَّلْ مِنِّي إِنَّكَ أَنْتَ السَّمِيعُ الْعَلِيم

Is it compulsory to follow the advice of a doctor?

Q: My question is regarding recent time of crisis when some of my fellow Muslims deny the lockdown and go to masjid. I try to convince them but need a proper basis. Somewhere I read, that it is mentioned in hadees, that If a person goes against the saying of doctor and eats prohibited things by doctor/expert which result to his death, it will be considered as suicide. Is it true? If yes, where is it mentioned.