When do I introduce my fiance to my Son's Father?

[rushy]

I have a 16 month old son, who's father is not involved in my life at all besides for visiting his son. We were never really in a relationship, just had "relations" and I happened to get pregnant, and gave birth to my beautiful baby boy. I have been in a relationship with a man, my current boyfriend, who was in my sons life before we started dating (was a family friend). We plan on getting engaged soon and I was just wondering what is the protocol for introducing your spouse to your sons Father? When should I do it? Before we get engaged? Once we get engaged? After we get married? My son's Father knows nothing of my personal life, and doesn't know I'm dating anyone. How should I go about this?

If it makes any difference, my sons Father is a very hostile and angry person. He has visitation with him every other weekend, but does not support his son and does not cooperate with my requests to co-parent together for the benefit of our son.

I also have a side question, what should I tell my son to call my current boyfriend when we get married? When we seem him, I just call my boyfriend by his first name in front of my son. I would never make my son call anyone but his biological father "Daddy" if he didn't want too. But since my son is so young, my current boyfriend will pretty much be "Daddy" to him growing. His Biological Father, is pretty much a dead beat.