I will def not breed him.
What are chances of him surviving?
This was our first duck hatch and he hatched all on his own and is sooo sweet .
He should survive; after all, he's already one of the lucky ones that did not die from the defect. That's not a guarantee, but, I would assume most that die after hatching would have died sooner than a fellow that size. But, I don't know for sure and can't guarantee it.
He's likely to be more easily killed by normal hierarchy squabbles, so he should be more protected like Silkies should, as it's the same sort of defect and carries the greater risk of brain injury happening under normal peckings that wouldn't hurt a non crested animal.
Lots more info here:
Ok so now I'm really confused . I'm also finding sites with crested rouens being sold? So they are selling deformed ducklings?
Yes. Not good PR to advertise that, is it?

Think of all the breeds that'd fall rapidly out of popularity if the bad points were advertised openly right beside the good.
But we're almost all guilty to some degree by creating demand for it, though often out of sheer ignorance, thinking it 'looks cool' or 'cute' or 'exotic' or 'special'.
Many, many whole breed types are established out of deliberately selecting for deformities and severe defects; in almost every single domestic species (and even in captive wild ones) we have selected for abnormalities, including often deleterious genetics and 'fixed' them into a breed trait.
Some examples off the top of my head:
Dwarves of most species including rabbits (look up 'peanuts'), cattle (especially Herefords), dogs...
Crested animals of some types e.g. budgerigars, chickens and ducks...
Dental/skull deformities, some of which affect the brain or are part of a larger problem, for example in 'pug'-nosed animals, from tigers to pigs to many dog breeds to some cats...
Deformities affecting extremities like ears (Scottish Fold cats) and horns (sheep whose horns grow into their eyesockets and faces), 'Spiker' deer, etc...
Feather/fur defects, like Chinese Hairless Crested dogs, Rex type cats, and Frizzle type chickens, 'feather duster' Budgies...
Muscle or growth defects like myostatin inhibition in dogs, Belgian Blue cattle, some commercial meat breed turkeys and chickens...
Abnormal coloring types of deleterious sorts, for example in Overo horses (look up 'white foal syndrome'), Harlequin Great Danes and Merle color dogs, white tigers, etc...
Nerve defects such as cause things like cretinism in all animals due to brain damage, epilepsy in ducks and dogs, creeping paralysis in dogs and rabbits, etc...
Bone disorders e.g. some which also cause creeping paralysis in dogs, skulls being too small so the brain is crushed when the animal outgrows its own skull (Cavalier King Charles Spaniel), etc...
Organ defects (almost all breeds have something under that heading), including heart cancer in some meat and layer commercial breed chickens, hereditary blindness and deafness in some breeds of dogs, etc...
Reproductive defects e.g. in Bulldogs, Dexter cattle (look up 'water baby'), also in purebred polled breeds e.g. in goats, Polycystic Ovary Syndrome in females and Spermiostasis in males, sperm deformities i.e. in Rosecomb purebred chickens, etc...
The list is a heck of a lot longer than that; this is far from exhaustive, and most of the breeds listed also carry other serious defects as well. All of the above are harmful traits, not harmless mutations; also, most come with more than one serious linked problem, including but not limited to lethality or suffering.
This is one massive reason why I really don't like purebreds overall, of any species.
Every species has lethal recessive genes, and once you start inbreeding to establish a breed, you're strengthening the likelihood of bringing afflicted animals into the world. Once you've made the breed, though, even outcrossing won't prevent it from happening, just lower the risk. In some cases they've managed to remove one or more seriously bad genetic traits but overall, you can assume if it's purebred it is almost guaranteed to be carrying at least one nasty heritable trait.
Every purebred dog has a minimum of one serious genetic defect, more often it's got about 4 or 5 serious, horrible defects in its breed, in fact dogs are pretty much the posterchild for having the most amount of the most severe genetic defects in any domesticated species.
Best wishes.