HI Chris, welcome to COL.
I'm no expert, but there are lots on COL who'll be along to help you.
Meantime, I'd say it's just your dog's preference for not wanting plain old dried food. What dried food is he on? I always add warm water to our dogs' dried food, and mix in a bit of Butchers Tripe, or real meat I've cooked, or sardines or something. What do you mean by "chicken gravy"? If it's chicken Bisto, then it's probably got too many additives and salt, but if it's "real chicken gravy" with flour as a thickener, then I can't see there'd be anything wrong with it. Your dog probably just thinks dried food on its own is a bit boring?
Regarding snails, I think I'd rather my dogs just ate snails now and again but definitely without the tabasco. Humans eat snails. I believe some dogs do eat their own poo, from what I've read on COL. although our dogs never have. Perhaps it's just a phase or perhaps he's not getting everything he needs from the food he's given?