I am very happy to hear that you have such a wonderful kitten, but rather discouraged to find that he has a heart murmur. It is true that many (if not most) times a kitten will grow out of a murmur but given the history of this breeder, and the fact that she refuses to provide you with papers or the parentage I would be quite concerned. If it turns out your new kitten also has HCM I would definitely NOT take another replacement kitten from her and demand a full refund and if she refuses, well then that is the time to consider legal action. Speaking of which, did you receive a new contract for this kitten, and did it address any differently what the recourse would be if he was found to have a genetic condition?
You know, being a friendly, likable person, only means she is a good sales person, it says absolutely nothing about the 'product'. If she has been producing sick kittens there is no excuse for her, no matter how nice she is!
As for a website to rate breeders, well that has been discussed before, but is rife with pitfalls. For instance, who will manage this site? Breeders? Pet owners? How can you assure that only people who have actually purchased from a breeder is rating this person (and not all of their family members and friends as well)? How do you weed out the disgruntled pet owner who is unhappy because (as an example) their seven month old Savannah has now started spraying because they never altered it, but now want to return it to the breeder for a full refund? I have thought about having a rating system such as eBay has but still - someone has to take responsibility for it, including handling any lawsuits filed against the site by breeders unhappy with the ratings they have received.