I don't know if what I say will be helpful. I am a birth mother, but I can only talk from my own experience. I found my bson when he was 31 almost 32 because he had registered on adoption.com sometime before. We have been in reunion for 12 years now. Crystal, I'm so sorry your birth mom tried to issue an ultimatum; I can't imagine doing that to my son and I'm glad his aparents didn't do that to him either. My Bson and I had a lot of communication in the beginning, mostly by email and facebook. (I remember exchanging lots of photos.) We have settled into a comfortable relationship at this point and I must admit that I am more often on contact with his wife. He has told me over the years that I can call him anytime but I rarely do, mostly because even now I'm hesitant about intruding in his life. He has a growing family and a busy job and I never know what is a good time. He is most likely to text me on Mother's day or our (mutual) birthday, etc. I tend to send ecards, etc. We do talk occasionally and my husband and I recently spend a long week-end with them.
I have found over the years that in any relationship one person tends to be the initiator most of the time. I have some relationships where I seem to be the one who always calls and others where the other person usually contacts me. I'm not sure why that it, but very few of them are 50-50.
Sigonella, I hear your frustration. It doesn't sound to me like your bdad really wants to avoid speaking to you. You are probably on the money when you recognize that this seems to be a very stressful time in his life. I suggest that you contact him occasionally (send him a "Thinking of you card or note) so that he knows you do want him in your life. Mention that you'd love to hear from you or ask when a good time to call is. That puts the ball back in his court. Hopefully you will have a long term, life long relationship with him. Your siblings will grow out of adolescence; he and his wife will eventually be a different time in their life together.
I hope you can hang in there, because it sounds like you could develop a good relationship with your birth family. It just won't be as quick or as easy as you would like. I have a cousin who always, cries out, "this is hard, cuz" when life doesn't go the way she thinks it should. One thing I have learned in my life, and it's been 45 years since I entered the world of adoption, is that nothing about adoption is easy.