Re: How to address Hz. Ali (RA)
^ I have heard that there are people who actually ask Imam Ali (as) himself for help, like Alawy or Nussairy, but I am yet to meet somebody like that. This practice is wrong and Imam Ali (as) himself warned against such fallacy.
However there is nothing wrong with beseeching Allah (swt) in the name of His beloved personalities whom He showered with his greatest favors. Its the concept of Tawassul, that is proven from the Holy Quran, Seerat, and the sayings of the Prophet Mohammad and his purified family, peace be upon them.
You asked about the obstacle- the biggest obstacle between us and the Almighty is the impurities and the sins that we have commited.