I guess this is one way to pitch Emily's book; make the whole column about dogs - of one sort or another.
1) Obviously, neither of you are going to yield on this. I'm guessing you had the dog before you had him. Find a guy who actually likes dogs. Even in your 40's, this isn't as hard to do as you might think. In fact, a dog is a much better way for a woman to meet someone in public than a child would be.
2) I think your husband has been more than patient. He still is, since he's leaving the choice to you. The reason the rescue societies want people to return pets to them, is so that they can make a better match for the pet on the next try. Prolonging it just makes it that much harder for your dog to adjust to a new home.
3) When people try to fix you up, tell them you are already in a relationship, and would prefer not to discuss the details at this point. Has this woman been severely disabled for the entire 20 years you've been together? Do you know this, or is it just what he's told you?
4) Is she being overly sensitive about being pregnant, or have you been overly sensitive about people who only "want to talk about ... play groups and strollers"?