Honestly, it sounds like this vet is being very thorough. Some vets are not so great about a lot of questions...and maybe you will find one you like better later on. For now, I think he sounds like he is on top of things.
Pancreatitis to a vet is pretty cut and dry....the dog needs his tummy rested and his body as well. Rest and fluids.
Homestly, the last thing to worry about is exercise and what you will feed him when he is better. Priority number one right now is to get him past this illness! That is what this vet is focusing on!
Subcutaneous fluids are often used. My vet prefers a longer hospitalization at the start with IV fluids because what is happening to Jackson is what often happens. It takes a bit longer for the levels to improve when using subcutaneous fluids.
You certainly could make an appt with the other vet if it makes you feel better but I personally think it is a bit of a waste of money since this is the standard of care that the vet is offering. Just my thoughts...and hey, it's your pup and your money!
I would stop long walks and help him learn to be a bit of a couch potato for now!