First off, vets don't understand crap about nutrition, so take what she said with a grain of salt.
As far as weight, when you started exercising him more did you increase his amount of food? You need to do that because they burn calories faster.
As far as the pancreas, it is Exocrine Pancreatic Insufficiency, or EPI. Why would your vet think he has this? Does he have foul poop that stinks to high heaven and looks like a cow patty greyish in color? Has he lost a good deal of weight in a short period of time? Does he scarf down food like he is starving to death?
How many ribs show on your dog? Do you have a picture you can post?
Also, EPI your dog would be a voracious eater of feces. From what I've heard of the description the dog is starving to death; and acts like it. (the sick dog---not yours *wink*)
As far as Raw, if I had the freezer space I'd do it.
I've yet to hear of a vet (locally where I live) that says anything good about it....their big issue is usually salmonella....Um, I don't know, I don't even leave the kibble bowls down. I pick them up and wash them; why in the good Lord's name would you leave a bowl with raw meat sitting out for hours.
My girl was very thin as she was younger; when she hit two, she started having seizures so the drugs really slowed down her metabolism.
I only have to feed her about three cups of kibble a day as opposed to 6-7 cups.
I'd still get that "what'ya feeding your dog?"
I did find though EVO was a good food; it was too high in protein for such an ampy dog with no job. When I switched to a lower protein, and something with some carbs she put on some weight.
As far as the ammount, if you dog finishes eating and keeps going back to the bowl and checking after being done; it could probably handle another 1/4 cup or so. I've actually uped my dog 1/2 cup a day before; just depends what we've been doing.
Gotta love the dollar store measuring cups.
ETA: I have gone through two vets before finding the third vet that is good with Alice and doesn't treat me like an idiot. Or, the assistants afraid of large dogs. You can fire your vet; it's OK to do that.