Conveying the reward of good deeds to the deceased

Q: Recently a woman's husband had passed away and on a ladies group we are all on someone asked for those who wished to read a para or more. She used the word "khatham". To my knowledge it is bid'ah as the Qur'an is for reading, pondering, listening, learning from (amongst other things) and not for giving reward to others as there has been nothing to show Prophet Muhammad (sallallahu alaihi wa salaam) or his Companions did it.

Please advice if it is correct or not.

Preparing food and eating in the the state of janaabat

Q: I had ejaculation last night and don't have ghusal. I have 3 questions:

1. If I wear clean clothes, do they become impure (naapak) if my body has sweat and my clothes become wet as my body is impure (naapak).

2. If I drink or eat something without ghusl will it be haram?

3. If I prepare food and wash my clothes with water in this condition will both of these things become impure if I dont have ghusal?

Zakaat on cash

Q: My question is about nisaab of zakaat on cash only.

I do not have any thing like gold or silver but just some cash. Please tell me on how much cash will I be liable to pay zakat. Will the nisaab of gold apply as cash is an alternate to gold in banks? 

Remarrying after khula

Q: I have a elder sister, she had taken a khulanama and talaq e bain as per Indian juridical in the year of 2015 and she also taken a custody of her 3 year son at the time of Khula and from now they are living separate.

Now her husband wants to remarry with her and he is saying I didnt say a word of talaq and since you wanted khula so I just signed and my intentions were not to take khula.

After they get khula my sister didnt perform the iddat period and she is just living a life without a husband.

Now they both want to remarry, can they remarry in Islamic laws.

One more thing, on khulama paper it was written that khulanama and talaq e bain irrevocable what does that mean?