Chicken by products.. that has so much variety (ie could contain non denatured drugs and other things in your typical 4D meat.. not what I would say is easy on the digestion)
No more than regular meat would contain, and the same chicken muscle has as much chance of being from a '4D'/drug residue animal as byproducts do. Your stomach, even in a previously starved dog, does a good job of denaturing proteins, it's what it does.
Protein sources won't matter too much as primary energy sources in starvation are carbohydrates and fat. In a cat, sure. In a dog, not so much.
Whole grain corn may be more difficult to digest than just corn starch on its own, but I've not seen anything to indicate that it's significantly harder to do so. If you have something that says otherwise, please share.
Most people I've seen claim this do so because it has higher fiber content (and thus produces a larger stool) and that's mistakenly thought as "oh this dog isn't digesting this as well", which is true for the insoluble fibers (hence it going out into the stool), but not the stuff inside the corn itself. It's already been processed, so it's not like you're just giving them whole kernels of the stuff. You can even look it up on that
DogFoodProject site I see people cite a lot.
Corn often gets an undeserved bad reputation. While it is not acceptable as a main source of protein in a dog food (as it is used in combination with corn gluten), as a source of carbohydrates it is no better and no worse than other grains in terms of nutritional value and digestibility. The starch part of corn is highly digestible but the whole ground product has a higher fiber content than other grains (around 7%), which results in slightly larger stools - often incorrectly interpreted as lack of digestibility. Unless an individual dog is intolerant or allergic to corn, there is no need to avoid products which include it in reasonable amounts.
But if you don't like a specific ingredient, then find a food that doesn't have that one; there's plenty of different brands and formulations out there.
Also dried egg product is defined as:
Dried, whole, cooked eggs (minus shells) are often added to pet foods to increase the protein biological value. Raw egg whites contain avidin which binds to biotin (B Vitamin) to make it unavailable to the pet.
It's just another protein source.
Additionally, though 'highly digestible' (of which i/d is one) is not a protected/regulated term, it's traditionally been reserved for meals that have protein, carbohydrate, and fat digestibilities of >85%. That percentage will vary in a previously emaciated dog, but so will others.
Some will say I'm plugging i/d: I'm not. I don't care what she feeds her dog as long as it works. But i/d is a good comparison if you're looking for a similar food. And from my experience, it works very well in handling animals with GI problems, including starvation.