i'm so sorry about your loss, i hope jack will be ok.
I had a similar situation, i bought my dog from a place called California Pet's(which used to be petland)she was $1,900. I was really excited when i got her and brought her home (without my parents knowing i bought a dog). When my mom came home she saw her and first yelled at me for buying a dog and then she said i bought a sick dog, because Molly was just laying down. The next day i took her to the vet ("their" vet) i went there because they said it was a free checkup if i went within the first 3 days of purchase. Molly had an upper respiratory infection and was hyperglycemic and she ended up staying their for 3days. The vet bill was like $800 so my mom called California Pets but they said they couldn't do anything about it. My mom found out that the owner of CA pets owned the vet place too. So basically my mom called back there again pissed and threatened to call the news, they ended up paying for like $200 of the bill which wasn't that much but at least it was something. I learned my lesson and now know never to buy from a pet store again. But Molly is now almost 2 and is healthy and happy