You're welcome!
How much to give depends on what kind of product you're using - if you're getting the Nutri-Dench suggested above, dose 1ml per three pounds, once a day, over the bird's favorite treat.
The anecdotal dose for vitamin E 400iu soft gels is one capsule daily over treats.
This...
It is not normal for the head to be at such a constant angulation; frequently with ducklings, especially meat birds, this can be due to a vitamin deficit, most often of thiamine, or vitamin E. You could try starting on those two vitamins and note whether there is an improvement or not...