I am so sorry, that is devestating news.

Don't let your co-workers bother you. I know it's hard but remember you are an excellent dog owner and you know that, that is all that matters hon.

If you are not at all comfortable talking to your breeder perhaps a letter or email would be better? I have to say, this post is very well written. A phone call is more personal, and you will be able to resolve more that way, and faster too. Be honest with her, tell her what you told us, that you are not sure where to start. After that maybe say something along the lines like, Kirk is an excellent dog, he's really working out for us (IF he is & if you are willing to keep him despite this disease) but we've been noticing some problems.. (explain the symptoms you've been seeing) a trip to the vet confirmed what I have thought.... (give the details of the exam, x-rays, etc..) he has severe
HD.

Yous will be in my thoughts. {{{hugs}}} Good luck sweetie.