#3
In America the hanging behavior is typical of some genera of Dasypogoninae. Probably close to
Saropogon; I don't know what other, similar genera you have in India.
#5
Maybe you can start with this: https://books.google.nl/books/about/A_Review_of_the_Asilidae_Diptera_from_In.html?id=3B1DAAAAYAAJ&redir_esc=y
When i have more time i will have a closer look. I do not know much of Indian Asilidae yet :-)