Studying comparative religion

Q: I am a Muslim Alhamdu;illah and I try to learn about Islam whenever possible and read the translation of the Holy Quran and believe in the Oneness of Allah Almighty, the prophecy of Hazrat Muhammad (sallallahu alaihi wasallam) being the last prophet of Allah Almighty.

I also have a belief that the Torah, Injeel and Zaboor are also the Holy Books which are testified by Allah Almighty. But I also believe that the Torah and Bible have been altered or fabricated by Jews or Christians.

Kindly guide me whether I can read the translations of the Bible or Torah to know about the details about the history of various Prophets (alaihimus salaam) and to have a comparison where Jews or Christians fabricated the Holy Books.

I want to study these Holy Books for history knowledge as well as for comparison while having a strong belief that the Holy Quran is the ultimate truth. 

Qualities of an Imaam

Q:

1. I would like to know what are the attributes of a person being imam and leading salaah?

2. Can a haafidh who is known to exploit and be dishonest or is a substance abuser lead salaah; fardh or taraweeh salaah?

Intermingling attending colleges, universities and high schools

Q: A certain Aalim said that the intermingling which occurs in public transport and in shopping centres is in the same category as the intermingling which occurs in a high school and university. He said that the Deen allows this level of intermingling as a concession for necessities.

Please comment on this. Is it correct to say that the principles which permit purchasing necessities at a mix gendered shopping mall are in the same category of pursuing secular education at high schools and university?

If Zaid intermingles whilst on public transport to his halaal business everyday, what is the difference with Umar who also intermingles at high school or university everyday? Zaid is pursuing his Rizq directly whilst Umar is learning the skills in order to pursue his Rizq. Are both in the same category? Please may this be explained.

Fantasizing about actors and actresses

Q: If you imagine an actor, actress, or singer nude without any sexual feeling and without any sexual attraction. In other words you don't have any sexual intention or feelings towards them. You don't have any intention to insult or disrespect them but you think with your mind, how would x actor/actress or singer look like if he/she was nude. Are you considered to have insulted him/her? Are you considered to have disrespected her/him? Are you considered to have done an injustice to her/him?

Is this similar to insulting your schoolmates with dirty words? Is this similar to disrespecting your schoolmates by insulting and offending them and saying bad things about them? Will you pay anything to them on the day of judgment based on the Hadith that says that their good deeds will be given to the ones they have done injustices.

Choosing not to get married

Q: Is that person sinful who does not marry in this world if he/she does not find someone as relgious and God fearing as him/her in this world and wants to remain unmarried to marry somone very pious/God fearing in the Hereafter because a more religious/God fearing person will have better rewards in Paradise and would share them with his/her partner.