If the nostrils are clear, it's ok. It takes a long time for a duckling to absorb the yolk. If you candle the fat end, you may be able to see a reddish pinkish area that is yolk. When it's absorbed it glows more yellow down there. It's better to leave it a bit longer to be sure than to do it too...
Chickens can grow at different rates. You said it's bossy so it might dominate the food bowl. In the end, it'll all work out and they'll be around the same size.
Ducklings are a pain so I've had a harder time with them. 1) they need more humidity at the end. 2) they need more patience as they hatch slower than chicks.
I'd wait until they are laying, if they're not. Maybe he views them as outsiders right now. My drake never took to a new hen I added. I finally decided to rehome the drake and get a new male duckling I can introduce when he's still young. My adult drake was good to his original 3 hens. But he'd...