blueheather- you are getting a really hard time here, it seems! I am a dog-lover- we had our dogs before our kids, and now, with 3 kids under 5, I find the dogs far more hassle. In my case, I couldn't rehome them (my old boy is 13 1/2), but I DO think you have done the right thing. It's not like you gave the dog to the nearest shelter, or abandoned it. As a vet, I see lots of dogs that would be far better off rehomed, but there is such a guilt issue surrounding rehoming, and there seems to be a "you made your bed..." mentality around, which is daft, as far as I can see.
All dogs are different- it's no good saying "you should have researched more"- that's like saying if you'd made sure your child was a certain star-sign, you would have been able to predict what kind of child you would have!! Some breeds do have distinct characteristics- what kind of dog was it you had?? If it was a border collie or a cross collie, they are generally very smart dogs and need a huge lot of time and attention, but you can have variations between breeds.
FWIW, even as a vet (who should therefore have a bit of an idea about cats! ) I adopted a cat from the surgery, on a trial basis. After 2 weeks I took it back. He HATED our noisy house- he peed and pooed everywhere and took to hiding away- not a happy camper. He was rehomed to an elderly couple who dote on him, and he them. Sometimes you need to do what is right for the animal, and if you are starting to resent the animal it won't in turn be happy.
People are being very harsh, I feel. Owning a dog, or cat, is a relationship. Sometimes relationships don't work out- otherwise we'd all be sitting married to the first guy we ever kissed! If you'd posted that your DH wanted you to himself all day, and you were frazzled keeping up with his needs, noone would have told you you should have researched marriage before getting into one!
You are also lucky you can still have a relationship with your ex-dog, and make sure she is happy in her new surroundings. I think it is much better all round