Hey--
Congrats on your first duck hatching attempt. I've only hatched a few batches, so I'm no expert, but for your basic questions:
Temp is the same for ducks and chickens. Humidity should be higher, but there is a great deal of disagreement as to exactly how high. Some folks run them at about 60% for the first 25 days and then switch to close to 90%-100%. That is roughly what I shoot for. However, I don't stress about it in the early stages. Mostly, you want to make sure that the air cell develops at an appropriate rate--not too fast, not too slow. I tend to let the humidity drop down into the 20s, then raise it back up by filling all the reservoirs, then let it drop again. I don't mist, but I've heard that it improves hatchability. I had about a 90% hatch rate with my last batch, and in the 80s with my previous batches. I used a lower humidity and higher temp (by 1/4-1/2 a degree--thanks to the inaccuracy of most thermometers on the market, you may have to play around a few times before you perfect your temp) on my most successful batch, and also did not wash them--not sure which was responsible for the higher hatch rate or if I was just lucky.
Don't forget that duck eggs take about 28 days to maturity, so don't throw them away after 25 days!
Ducklings will eat the same thing as chicks, but best to use an un-medicated feed. You won't need to vaccinate or worm or anything like that. They are very hardy. Also very messy--be prepared to clean your brooder daily.
By the way--misting is not designed to raise humidity. In fact, it has the opposite effect--I forget the science behind that, but in Storey's Guide he explains that it actually causes the air cell to develop more quickly. So don't try to substitute proper humidity with misting, or vice versa. On the other hand, you can have successful hatches with crazy humidity and no misting, so don't stress too much either way.
I do bring the humidity up near 100% at the end of the hatch. Basically, I just fill the incubator with as many sources of humidity as I can--sponges soaking in dishes, the tray filled completely, etc., just making sure the hatchlings can't access any of the water--and keep it wet in there. Usually the windows mist up a bit and the humidity gets up between 80-95%, but it continues to vary a lot as exterior and interior conditions change.
Good luck!
