That looks much better with the Vaseline! (hahaha that's a funny autocorrect!)
You did great! I'd leave him there for a bit, and watch for that vein to recede some more. It will get thin, like a thread. Talk to him, sing to him! You can even find youtube videos of other chicks/ducks chirping and play to him. He will rest some, then he may try to continue on his own, or you may have to help more. Just watch the membrane, we don't want it to dry out. And keep an eye on his bill, that he doesn't get it tucked under the membrane and not be able to breathe.
I'm not sure how much I will be on this afternoon and later. I have chickens hatching in 2 different locations, so I will be doing some running around. Go with your gut if you feel the duckling is in distress, but try to be as patient as possible. I know its a fine line. Hopefully one of the other tagged members will be around to assist too, if you need us.
** Oh, just saw your updated pic. I can see some dryness up inside the shell, just under your thumb in the pic. Chip away just a little bit more shell in that area where the membrane is not attached, and moisten that section of membrane too. If there's room to sneak a q-tip up in there, you can do it that way, without chipping more shell. Then I'd let him rest a bit.