If you believe going to Hajj now is a kind of helping the oppressors, yes.
Perform them two Rakas (as it was your duty during the journey).
If he used to forget the pillars of Salah, he can not stay as Imam. However if you mean by pillar, like Tashahod, Salam, Qonut, Zikr and Reciting after Fatiha, his Salah is valid, he can do sajdat al-sahw when remembr. But if he forgot pillars like Roku, two Sajda or Takbir, that Salah is not valid.
According to most of jurisprudence it is not najis.
The divorce is not valid because of the anger.
Moreover, according to some jurisprudence (Jafari) these 3 or 4 divorce should be in different times or sessions . In one session it is considered one divorce even if he says "I divorced you 3 times".
'The eleventh Imam, Imam al-Hasan ibn Ali al-Askari (as) reported that his Fathers quoted a well-known companion of the Prophet, Jabir ibn Abdullah, as saying: ‘The Messenger of God (s) said: “When God created Adam and Eve, they strutted through paradise and said: `Who are better than we?' At that moment they noticed an image of a girl like they had never seen before; from this girl came an illuminating light so bright that it almost blinded the eyes. They said: 'O Lord, what is this?' He answered: 'This is the image of Fatima, the mistress of your women descendants.' Adam asked: 'What is this crown on her head?' Allah said: 'Her husband Ali.’ Adam then asked: 'What are her two earrings?' God replied: 'Her (two) sons, they were ordained in My ever-existent knowledge two thousand years before I created you'”’ Source - Ibn Hajar al-'Asqalani, Lisan al-Mizan v. 3, p. 346.
