Hi and welcome to YT
. Congrats on your new little one! I'm sorry about your concerns with the breeder - believe me, many of us have been in your shoes too, so you're not alone. There are SO many unscrupulous breeders out there.
In her past pups where there are "sickly pups", what was wrong w/ them?
Even though she did have some sickly pups, your little one may be perfectly healthy - so I'd have the vet check him out thoroughly (check the knees!).