I'm no longer single, but I'm technically a newlywed, so I think these are still fresh enough in my mind to respond.
1.Does the fact that you're an Ex-Christian or Atheist affect your dating potential?
Absolutely. Not from their perspective, but from mine. I would not date a fundamentalist or fanatic of any stripe. I went on several dates before my now-wife and I started dating seriously and outspoken religious talk was a dealbreaker for me.
I can remember one conversation I had quite clearly. This woman was a knockout... blonde hair, green eyes, perfect skin, HUGE tracts of land on top of a tiny waist, was very well-to-do, and was the manager at my favorite pub. When she told me that she believe the Genesis story was literally true I told her, "I don't think we should see each other anymore." She was very confused and asked me what I believed about the beginnings of the universe, I told her, and she said, "Well, the bible is the word of god and that's just what some stupid scientists are saying. Who are you going to believe? You should come to my church tomorrow!"
I said, "I'll be right back." and I went to find our waiter. I paid for the meal, gave him a 20% tip, another $20 to bring her a cocktail with my apologies, and then I left.
As ditch-a-dates go, mine are pretty classy...
2.Do/did the women you meet or date/dated know about your de-conversion? Did you tell her, or did she find out through other means? (e.g family, friends, facebook, etc)
Several of the women I went on dates with knew me very well and some didn't. Generally the ones that didn't found out quickly that religiousity is a dealbreaker for me. I would basically ask them about their beliefs, listen quietly, and when they reciprocated I would give them the story of my deconversion. If their eyes glazed over, I knew religion wasn't a big deal for them. If they argued with me, I knew it wasn't a good fit and would take my leave.
When my wife and I started dating, we already had quite a bit of history. In fact, the first time I spoke with her, some eight years previous to dating her, we got in a huge argument about religion because she had the wrong idea about what atheists believed. At the time, she was dating a Satanist who identified as an atheist (less flak), so she thought everyone who was an atheist was a LaVeyan satanist. I corrected her and then bashed her wishy-washy, feel-good, never-thought-about-it christianity and an argument ensued. It was a while before we spoke again.
But yes, she knew I was an atheist before we ever started dating. Atheism is a big part of my life and I think it's important to be honest from the get-go about things that have the potential for conflict.
3.If you answered yes to question 2, how did she react? Did any of the women leave you or try and convert you when they found out?
A couple tried to convert me. I respond to conversion attempts on what I refer to as the "Dick Mode" scale.
"I respect other people's beliefs, or lack of beliefs, but I really think that my religion has the right answers because of a, b, and c." - Regular conversation.
"You should come by my church. We're discussing this exact topic!" - Disinterest Mode: Engage
"You should come by my church." (second request) - Dick Mode: ENGAGE SNARK
"You should come by my church." (every request after the second) - Dick Mode: ENGAGE CRUEL SARCASM
"But, if you don't believe this, you're going to hell!" - Dick Mode: ENGAGE CRUEL SARCASM, LEVEL 2
"I know where I'm spending my eternity. I'd like to see you there." - Dick Mode: ENGAGE CRUEL SARCASM, LEVEL 3
"You're not really an atheist, you know there's a god, you just want to sin!" - Super Dick Mode: ENGAGE
Regarding my wife though, after the major argument at our first meeting, we started discussing "safe" topics. Several years of friendship later, I was starting my life over with $400 and an overnight bag of clothes and she was very supportive. After things settled down a bit, we started dating and had the conversation all over again because I wanted to make sure that her theism wasn't going to be a sticking point, because I did have feelings for her.