...this is a great question, and I am so glad you shared it for others to see. I am so sorry you are coping with Efudex in addition to a lack of clear instructions. I can't imagine how frustrated you must be by this point.
Even with a thin layer, you can expect to have a good bit of itching and discomfort. It definitely sounds like you may have applied more than was neccessary, and I am glad you are dealing with the possiblity of infection. That is important when your skin is raw and exposed from the effects of Efudex.
I will just piggyback off what Sidney already suggested and say, yes, alternating Tylenol and ibuprofen helps a great deal with the pain. If you are struggling to sleep, I would recommend Benadryl (oral) for the itch and discomfort, as well.
As far as the nausea, I have heard many suggest using ginger. I know your sick feeling probably stems from the pain as much as anything, but ginger is a natural way to combat some of the nausea you may experience.
Know that we are here for you any time. I am wishing you well as you move forward. As Sidney said, we would love for you to keep us posted on our progress.
Sending you hugs! April, SkinCancer.net, Moderator