Calculations for altimeter settings for variations in barometric pressure
Question 1: 550 ft.

Question 2: 660 ft.

(rounded to the next multiple of 10).

Atmospheric pressure drops by 1 mbar for every 8.5 m or 27.7 ft of altitude between 0 and 1000 ft, and the differences of your cases from the standard atmosphere are small, so I did not use corrections.