How to contact (located) birth father?

Backstory: I'm a 22 year old woman, raised by my birthmother and her first husband, who married her when I was three and adopted me two years later. I always knew that my dad was not my biological father; although my step-parent adoption was not discussed while I was growing up, I remember the wedding. I remember being asked if I wanted to be adopted, and I remember choosing my name and going to the courthouse for the adoption to be finalized. My birth father has never been a part of my life. When I was in my mid-teens, my maternal aunt told me the little that she knew about my birth father, including his name. It was enough for me to locate him, though I did not do so until Oct. 2007, during my last semester of college. I was hesitant to contact him at that time, and wanted the confirmation that I'd found the right person. It was not a pleasant experience, but in Feb. 2009, I talked to my mother about my birth father; she does not know that my aunt told me anything or that I had already located a person. She did give me his name and mailing address--the same information that I had already found, so I got the confirmation I'd wanted. Since then, I've struggled with the decision of how and when to contact him. I have written about twenty drafts of a first contact letter, and I have a lot of anxiety about sending it (which I think is pretty normal.) His phone number is unlisted, but I do not wish for the first contact to be by phone anyway. According to my mother, he did not believe he was my father and wanted me to be given up for adoption. She has assured me that if I try to contact him, I will have the door slammed in my face. My dad, on the other hand, was initially a little hurt, but is fully supportive of my search. I am prepared (as much as I can be) for my birth father to be less than thrilled with any contact from me. I would like to believe that his decision not to parent came from being a scared 22 year old guy who got the rebound girl pregnant (as I've been told) and that he's fundamentally a decent person, but I'm trying not to have any expectations, in case this does not end well. I do not believe that his wife, parents, or other family members have the slightest clue that I exist. I anticipate that my contact will be a major shock. The Cliff Notes version of my letter (it's about two pages in full form): "I am [L]. My mother is [R] and I was born [when]. She has no doubt that you are my biological father. I understand your decision not to parent, and I'm not angry at you for it. I'm not trying to destroy your life by contacting you. I don't want money or for you to put me on your next Christmas card. I just want answers; I'd like to know medical information and, due to my interest in geneaology, family history. I understand that this letter must come as a huge shock and that you will need time to process it; it hasn't been easy for me to write either. I have not contacted anyone else in your family, because I believe that you should have the first opportunity to do that, in the way you see best. However, if you are not prepared for me to be in your life at this time, I respectfully ask that you give your mother & family the information needed to make that choice for themselves. Here's how you can contact me." (It sounds much less flippant in the actual draft, of course. The big things were that I wanted to assure him that I'm not after anything more than information, and that I have considered the effect that this letter and situation will likely have on him and that I'm not angry at his decision not to parent.) I think I'm also going to include a picture or two. A few concerns I have: if it's true that he didn't believe he was my father, should I offer to go through DNA testing in this letter, or see how he responds to the first contact? How much should I say about myself? I think it's probably best to stick with the basic facts I've given in this draft, rather than giving off the "look at all the great things about me, now love me please" vibe--why offer any more than name/birthdate until I know he even wants to know it? I am planning to send this letter certified mail w/ return receipt information so that I know he received it, but how long is reasonable to give him to reply? The only time I've ever felt angry in this whole experience was when I learned that my biological grandfather had died without me ever having the chance to meet him. I do not want this to happen with any of my other biological family, and I do believe that his mother has the right to know that she has another granddaughter and make her own decision about whether to know me. I have contact information for his mother, all three of his siblings and their spouses, and have located two aunts, as well as my sister (!!) on Facebook. My sister, and I suspect a brother, are both minors. For that reason, I will not contact his other children if he chooses not to respond to my letter, but would it be wrong of me to send a contact letter to my grandmother if a reasonable amount of time passes without a response from him? I'd just appreciate any insight or advice anyone can offer. Does anyone have any experience contacting birth fathers who knew, but hadn't told any of their family? How did that go? I'm also worried about his wife's reaction--I can't imagine the pain this might cause her, and his kids--goodness knows they've probably got enough general teenage angst without finding out about their father's other child...I know that there's never going to be a way for me to know that this is the "right time" in their lives for me to make contact. I know this is the right time for me, so I'm just trying to do everything I can to make this first contact as "right" as possible. I only get one first impression, after all...