
If you feel safe doing a water crossing, than a 40lb dog should not really have too much of a problem either, especially if it is a good swimmer. You could hook them up to a line (like someone else mentioned) if needed. Definitely take off their pack and attach or put in yours.
Our dogs love fish too and have often caught fish to cook just for them. Regular dog food along with dog treats or doggie power bars, go and end up in the canister at night with all the food. Side note: sometimes a dogs appetite can change while hiking--sometimes they won't want to eat the food they normally eat and/or sometimes they eat a lot less than at home. Just something to watch.
Compared to others on here, it sounds like our dogs sleep in luxury since they have their own down sleeping bag and pad. A fleece jacket might work for your dog but don't be too surprised on a chilly night, waking up to a cold wet nose digging for warmth in your bag.
