NOT A TEACHER
I have checked Mr. Michael Swan's very popular Practical English
Usage, my dictionaries, and the Web. I may have an answer.
(1) I most respectfully suggest that you are correct and that
the proofreader "accidentally" made a mistake.
(2) I believe that it is good English to say either:
(a) This job requires sacrifice. (sacrifice used as an uncountable
(b) This job requires a sacrifice. (sacrifice used as a countable
(3) If you wish to add "too much," you would then get:
This job requires too much sacrifice./ This job requires too much
of a sacrifice.
(i) Mr. Swan points out that we may use "much of" before a
determiner (such as "a" or "the"). His examples:
You can't see much of a country in a week.
How much of the house do you want to paint?
THANK YOU & HAVE A NICE DAY
P.S. Our wonderful Mr. Swan also has an answer to your last question.
I haven't got much time. (He adds that "much" is usually used in
questions and in the negative. A lot of is more natural in the
affirmative. So I guess you should say:
I've got a lot of time. / I have a lot of time.)
Student or Learner