While some of what you said has some good information.
Read the following so that you can arm yourself with facts. The following is written in plain english so that it is very understandable.
http://www.yorkietalk.com/forums/yor...-answered.html
Has a lot of info, but there is more.
Read a thread in the Sick and Injured forum. A pup that is very ill and might not make it, she is a result of a cross breeding. Her multiple diseases were passed to to her by her parents, so she got the worst of both breeds.
You can also inform him that being the stud owner, he is just as responsible for anything that may go wrong. He is also responsible to take any pups that can't be placed or any that are returned.