I know you love him, and are worried, but it does sound like he is improving.
Severe pancreatitis can take 2 weeks to resolve. So I would expect a mild pancreatitis to improve in 2-3 days once treatment is started.
If he were my dog, I would also start him on 1/4 of a 10 mg Pepcid ac tablet every 12 hours. The Pepcid is a human stomach acid reducer that will help decrease any excess acid in his stomach from antibiotic, pancreatitis, or not eating. That should help with his appetite as well. You can buy the Pepcid at any human drug store or grocery store.
It will probably take 2-3 days until he is eating as usual.
If he refuses to eat at meal time, you can help keep his blood sugar up by putting a few drops of honey, karo syrup, or pancake syrup in his mouth.
If he starts vomiting again, refuses to eat or drink for more than 12 hours, or he is very painful when you press on his abdomen under the ribs then he should see a vet.
I hope this helps.
If you have additional questions, please reply.