Unfortunately Kimbertal has absolutely NO reasons to be charging that price. They are one of the biggest known puppy mills in the US for Dobermans. They con people into paying those prices without appropriate health testing. They have "results" listed but there are no numbers to check those results. There should be OFA numbers that are verifiable through the third party (OFA) the back up their claims. Anyone can type a disease and then type good or clear after. The biggest red flag is that they let anyone take a female (for free), then raise her, then bring her back to be bred, birth puppies, then deliver the puppies back to Kimbertal at 7 weeks of age. Puppies should never leave until 8 weeks firstly, second of all.... WHAT? Ethical breeders would NEVER allow this. Another red flag is they breed two different breeds. You don't see this often with serious preservation breeders. They have a breeder form right there on their page to be a breeder under them with their dogs. They also don't have questionnaires to get to know buyers. They will send dogs to anyone with money. No ethical breeder does this. They want to know where, and to who, their puppies go. They don't appear to have contracts form the buyers to prevent back yard breeding. It appears as though every dog goes home with full registration. Again not something you will ever see with a proper breeder. I list all of this out to show you what to look for in the next breeder. No one should have to see the issues you have with your dog at such a young age. It's not uncommon from this breeder, though.
They import European dogs from "titled" parents (I put titled in quotes, because many of those titles are not through reputable venues and are rumored to be bought and paid for) then coast off those titles. They are not proving their dogs in any way. Even under their past stud dogs there are dogs with no titles. (titles are a third/unbiased party confirming that dogs are a great example of the breed and should be bred) I'm very sorry you fell victim to them. It is not your fault. They are predatory and it takes a lot of time and reading to find a true ethical/preservation breeder. I would start by going to the DPCA website and the breeder referral section. You still need to do your due diligence, but many there are amazing breeders. It is broken down by state.
If you have any questions about a particular breeder, come here and ask. We will be happy to help in any way we can. Many preservation breeders here will tell you that they see no where near as much DCM as the reported 50% number we see thrown around everywhere, because they are actually testing for the disease appropriately and following pedigrees, and looking at longevity in the pedigrees they are considering breeding with. My breeder has a dog that just turned 13 years old recently. Another breeder here just had a litter that was (frozen semen) fathered by her dog who lived to be 14!
As others said before, there are no guarantees, but an ACTUAL ethical breeder will give you the best shot you have for great health and longevity. I hope you stick around and find a great breeder for your next companion. I also wish the best for your current dog. I hope you can find a vet or specialist that can do something for the quality of life and give him many more happy years with you.