Any advice for a special needs duckling

This is Rivet. She* is 10 days old and one of 27 ducklings from her nest. Right now, I'm raising her indoors because she has a bad twist in her spine that essentially makes her hunchbacked. She was knocked out of the nest when she was still wet from hatching. After three days in the indoor brooder to get strong (and have her neck and splayed legs braced) she went back to the nest with zero issues--the moms, despite having rejected her once, took her right back in. Two days later she was being picked on both by moms and siblings. More than once I saw her stumble and then get trampled over by the rest of the ducklings. At that point I decided to bring her back indoors.

Problem 1:
Her oil gland is healthy and functioning, but because of her hunch she can't reach it. She also can't reach much of her body to preen, so she winds up performing the preening action in empty air. Are there any safe oils that I can brush or mist over the baby fluff (and as they come in) the adult feathers to keep her plumage healthy? I am concerned about her not being able to waterproof herself, and that if she can't reach the oil gland long-term that it may clog or dry out or get infected.

Problem 2:
I have two more duck eggs that were "contributed" by other ducks to the big nest but that happened two weeks behind the rest of the nest. I put them into the incubator for about a week when one of my chickens turned broody. I don't have a rooster for her, and she was trying to set on all of the other chickens' eggs (the girls were all convicted of aiding and abetting). I had the bright idea to try giving her the fertilized duck eggs. She immediately got with the program and decided that they're her babies. My hope is that once these two other ducklings hatch (they're piping today!), I'll wait another day or two and then try to introduce Rivet to this nest. Has anyone introduced a different duckling to a nest that wasn't their original group? My hope is that since she's two weeks older, and therefore will be bigger and stronger than the two new ducklings, they won't be able to bully her. I'm pretty sure she won't be interested or able to bully them, either. That way she'll have a bird-mom and other ducklings to socialize with like she's supposed to have in the first place.

*I actually have no idea about the duckling's sex; I just smacked her with a pronoun for my own convenience. If she turns out to be a he we'll cross that bridge when we're halfway over it.