Re: How to address Hz. Ali (RA)
Nosherwan, its all in the intention. Any act or ibadat can be voided if the intentions are not pure.
It is a great practice that you directly ask Allah (swt) to help you in time of need and listen to your supplications and so on. But intercession, through people whom Allah (swt) has elevated, is a highly acceptable practice in Islam. In the Holy Quran, there are many verses on this topic and several events from the lives of the different Prophets also confirm Allah's likeness for this practice.
An argument present against intercession is that; Prophet Mohammad, Imam Ali, Lady Fatima, etc are with us no more therefore its wrong to ask them for help since they can not hear us nor they can help us in anyway.
The answer to that is that Quran states that even those slain in the way of Allah (swt) are not dead, and I consider the status of the chosen people of Allah (swt) much greater than that. Loving them is a command of Allah (swt) and sending blessings daily to them is an obligation for a believer. Would Allah (swt) order us to love and send salaam to some one who is not even able to answer us or help us?
By the way, both the Jews and Christians are divided on the permissibility of intercession.