FWW -
Q1: I guess it is better to have it de-iced than not?
Q2: I ALWAYS enter the OAT on the cdu regardless of type of 737 on the basis that if the TAT system failed and ran away 'high' I would always have the right MAX N1 if I needed it. Remember that 99% of the time you are running at a 'false' OAT on reduced power, so failure is not a problem.......unless you are full power or engine out.