Really sorry to hear about your cat(s) and how ill they have been.
Your post is quite confusingly written. As I've read it: you have three bengals, all from the same breeder. The first two bengals have had various serious health problems, but you still bought your third bengal from the same breeder? The third kitten died after falling ill, the breeder was a bit defensive about it, but offered you another kitten as a replacement and you refused it. You think the cats are ill-kept and want to report the breeder. Do I have that correct?
If you think the cats are being kept in way that seriously affects their welfare, then you can report this breeder to the RSPCA. Legally a keeper of animals must provide: somewhere suitable to live, food and fresh water, space in which the cats can exhibit their natural behaviours, and protection from illness or injury.
If the cats are registered with TICA, then you can report them to TICA though this seems to cost quite a bit of money:
http://www.tica.org/members/faq/complaints.php I'm not actually sure what this would achieve, maybe someone else can comment.
You could also try the "bad business" route, and speak to Citizens Advice Bureau or Trading Standards. They could give you advice on what can be done after being sold a sick animal. Just a note though - the breeder was right to offer you a replacement kitten. I know emotionally you may not want the kitten, but from a trading standpoint it was the right thing for them to do.
At the end of the day though, it is imperative to research breeders thoroughly before purchasing. It is not illegal to thoughtlessly breed cats, and so bad breeders may be within the law. All you can do is not buy from them.