Is it appropriate for a doctor to use emotional language such as "i'm very upset" in a message severing their relationship with the patient?

The language you are describing would need to be put into context to determine if it is appropriate or not. Hopefully, you can find another physician who can meet your needs. Sometimes, the doctor-patient relationship doesn’t work for one reason or another. But, usually it does so seek another physician to care for your health needs. Good luck to you!