Associating with shias

Q: At our University we have Salaat al-Jumu'a in which 85% of the followers are of the Ahlus Sunnah wa al-Jama'a and 15% are of the Twelver Shi'a. The Shi'a stand in our Saf (rows) and pray with us. They do not bother us, nor do we bother them. But at the end of the day they are Shi'a, so should we the 85% tell them to leave and not pray with us? 

We have overheard their discussions in which many say wrong ahadith/rewayat, but their leader on our campus I have heard many a times scold the Shi'a and say that Hazrat Aisha is our Mother and is to be respected even if she made a mistake. Their leader keeps them in check. So are they Muslim? Can they pray with us?

Seeking forgivness

Q: How does one rectify one's shortcomings in Huququl Ibaad particularly when the concerned person has died. For example one had been disobedient or has hurt the feelings of his parents and the parents have died?

Reciting Sami Allahu liman Hamidah instead of Subhana Rabiyal A'laa

Q: When performing Salaah behind the Imaam, in the sujud after saying a few times "subhana rabbiyal alaa" somehow I was about to say "sami Allahu liman hamidah" but as soon as i said "sami Al" I realisized and cutt off and continued saying "subhana rabbiyal alaa". Now was my prayed invalidated since I cutt of at the half? Must I repeat it?

Taking one's naffs as one's ilaah

Q: My question is about an ayat in a quran that says, "those who take there nuffs as there illah". What does this ayat mean? 

Can it be possible that  a person goes to his wife, and be worshipping his nuffs even though he goes to his wife and has intercourse in a  way allowed in shariah. What if he is behaving like an animal or acts upon his animal qualities. Is this allowed in sharia? I am not married yet but I am afraid to get married because of tasswuf and wazifahs and the effects they have upon me.

Obtaining the intercession of Rasulullah (Sallallahu Alayhi Wasallam)

Q: What is the reference for the following Hadith and can we tell people the virtue contained in it?

The Messenger of Allah  (Sallallahu Alayhi Wasallam) has said ‘whosoever recites ten duroods upon me in the morning and ten duroods in the evening, my intercession will definitely reach him on Day of Judgement".

Could you explain the reference of this Hadith and whether it is authentic?