Will preventing someone from walking in front of one while performing salaah be considered amal-e-katheer?

Q: It is written in Behishti Gohar that it is allowed to prevent a person from crossing in front of him while he is praying. However, if 'عمل کثیر' happens, then the prayer will become fasid.

What will be considered عمل کثیر ? What should the musalli do to prevent the person from crossing him?

Intention when making qadha salaah

Q: Regarding qadha salaah (missed prayers):

What is the full intention to make before one performs a qadha salaah (Note: the intention for ample salaah missed not just a single salaah). I am fearful that if my intention is incorrect my qadha salaah wont be accepted. Many books have the intention for only missing one prayer. 

To my knowledge the intention is "O Allah, I am reading the 1st fajr of those that I have missed" but I am unsure if it is correct.

Woman living alone

Q: I am a Muslim woman. Currently I am going through a lot of troubled times as I lost my job in Dec 2018. I didn't want to be a burden to my parents so I had taken a house for rent close to my office and have been staying alone even after I lost my job. All this while I managed by some savings I had. Now I desperately need a job to pay my rent and bills. I have been worried and praying to Allah. In the house where I stay, it has been 2 years that I am here but had never heard azan till now since there isn't a masjid nearby. But today, all of sudden, I heard azan between Magrib and Isha time. I'm sure this wasn't Magrib or Isha azan. I was surprised to hear it as it is the first time in 2years I have heard it. Can this mean something? Is it some kind of a sign from Allah? What does it mean?

Earnings of an insurance broker

Q: My father works in an insurance company which is being run by Muslims and follows Muslim laws. He himself is an insurance agent who does insurance of different people and the more people participate, the more commission he gets. I want to know whether the money he earns is considered halal? Because the insurance policies he introduces gives that person money time by time.