Is this situation an example of vet negligence? My pet died from lack of information.

My dog had huge surgery to remove a spleen due to an eruption. The vet let me know it was fine to take him home within the next day. They released him despite not figuring out what the right pain dosage was for him yet, and wanted me to experiment at home with different dosages of codeine and gabapentin. Upon further research, I read that codeines specifically does not interact well with animals with certain health conditions such as hypothyroidism and liver issues, both of which my dog had. My dog couldn’t take Codeine and kept throwing up from the medicine, and he ultimately had to go back to the vet and died within an hour due to blood clot. Upon further research dogs with hypothyroidism are at an increase risk of blood coagulation. The vet did not communicate any of these risks to us and did not proactively provide ways to mitigate blood clots (exercises and movement to create blood flow, compression stockings). There are ways to help mitigate risk of blood clot and none of his was told to us, despite my dog being older and higher risk with his thyroid issues. The vet denies they did anything wrong but I believe they were negligent with providing all the information possible to mitigate risk of blood clot, especially cause my dog is at a higher risk with his health issues. They did not provide any communication on risks to take him home only 1 day after surgery, all the while on undefined pain management solution. They said nothing and said they were comfortable with me taking him home. I called them to let them know my dog hasn’t eaten for 2 days and they told me to get more anti nausea medication. Codeine specifically made him nauseas and not have appetite. Yet we weren’t told to try other pain meds. I am requesting a partial refund which they are denying and now they are asking for another 2k for the 1 hr spent of him dying at their clinic. I am not going to pay that additional amount and I want to dispute a portion of their 10k bill. Is the vet negligent here? What can I do? The vet was unwilling to address my concerns with them specifically not giving him a proper dosage, letting him leave in a day, as well as not communicating blood clot risks and techniques to prevent it from happening. I would have tried all to take a proactive approach to mitigate potential risk… Also the night we were grieving in the back room shortly after my dog died, one of their vet techs came in with her credit card slider and directed us to go over costs. She had an extremely condescending and rude tone to my response of being upset and that was traumatizing. Thank you in advance for any insight or guidance.