Good luck to you, and I hope everything turns out simple, easy, and you can enjoy your pups.
Regarding your motives, as you said yourself, it is a moot point and you came asking for help, not a psychiatric analysis of your conscious and unconscious desires based on a simple post that will logically not include every single detail of the situation and every single listing of the things you did to prevent what has happened. I also kind of took a step back when I saw your comment about seeing the tie and just letting it go, but stopped myself. Why? Because of common sense. I know that if I had been taking all the steps I knew to prevent them being together, AND I had come upon an inexperienced male and female already IN a tie as you described, I know that attempting to break that tie could cause severe injury to both dogs. So no, I would not have tried to stop it either at that point.
Regarding the judgments you've received on having them tie again due to the information you researched on having just one pup, it sounds like you did what you thought was best, now that the barn door was shut after the horse got out. Bravo to you for your honesty and attempt to prepare for what will happen. We all weren't born with an encyclopedia of knowledge for the dog, and I would like to gently remind others of that...we learned it through mistakes, trial and error, and research. Several posts here have given very good info for you to check out, which it sounds like you are doing.
Please keep us updated on how this works out. And be prepared, as another post pointed out, that sometimes family adoptions DO fall through, so do what you can to be prepared and have the pups tested as needed if you DO have to make an outside adoption for some of them. Hopefully it will be a small, healthy litter and your percentages of having to do so will decrease.
Best of luck...you definitely are about to get a learning experience
~Twitterpate