Issuing three talaaqs in the absence of one's wife

Q: I constantly have waswasa regarding different things, such as fears of losing important things and intrusive thoughts about divorce. 

Recently, while driving alone, I had thoughts of talaq, and I became worried about accidentally uttering the word and losing my wife. To counter these thoughts, I ended up saying the statement three times "main tumhy talaq deta hon" with my wife's name, thinking it would stop my mind from repeating it in front of her. 

However, I later read that divorce in isolation might still be valid. I also consulted an Imam at the Masjid, who assured me that the talaq is not valid. I would appreciate your opinion on this matter.

Student in a boarding school sleeping in a place safe from sin

Q: I go to an all boys boarding school, and in the dormitory, when it's time to sleep, there are many boys that watch movies in the rooms, and they do all other sorts of Haraam in the room. 

If there is an alternative place for me to sleep, such as a close by Masjid, or the library, is it permissible for me to sleep in the dormitory?

Businessman preventing two people from transacting a sale on his property

Q: Could mufti advise on the following: 

Person A owns a Cash n Carry, person B and person C both are his customer's and purchase from him. At the premises of person A, person B and C meet and start transacting on person A's premises. Person A in turns tells Person B that person C is my customer and you cannot supply him. 

1. Is this type of clause permissable in shariah where person A stops person B from supplying person C as he feels it's his customer. 

2. If person B and C transacted on person A's property, is the sale valid.