1- The actual incident is not weak. There are many clues that confirm it.
2- Yes she was martyred. You may find many hadiths from Sunni and Shia sources here that confirm that:
https://echo-najaf.blogspot.com/2021/01/blog-post_24.html?m=1
https://www.aqaed.com/faq/4685/
http://qadatona.org/عربي/الوقائع/166
3- Here the hadiths of Mohsen:
https://www.aqaed.com/book/531/2/
4- Yes most Ayatollahs believe it happened.