I would go no higher than 75% on the humidity. If you are in a humid area, I would actually go even lower. If you can leave the vent all the way open and maintain temp/humidity, that is what I would do. More fresh air in is good.
IMO, I do not go above 70%. I found I have more hatch if I don't go above that. Sometimes I think to much is not a good thing. I like to dry hatch mine, I do better with that. Good luck
I've had mine at 68-70% and with each one that hatches it goes up to 75% I vent a little to about 70-71 %. I find that when it goes to about 75% you get condensation on the windows. Which could cause a lot of condensation in egg cell and drown your chicks. good luck have a great hatch