You don't realize how fast Cairo has grown since 1950. Trust me on this. Ditto for Alexandria.
Again, these cities have grown tremendously since 1950. You can't go by current population figures at all. And some of the figures you're quoting I know aren't completely accurate. But again, (for the third time) you have to consider how fast third-world countries have grown in population, especially urban-population, since 1950. While Europe and North America have been MUCH slower or have even declined some in the same time period.
And I can name you 10 metro areas larger than Cairo today. (and I know there are a few more)
Tokyo, New York, Mexico City, Osaka-Kyoto, Sao Paulo, Seoul, Bombay, Shanghai, Beijing, Los Angeles. (these are NOT in order, but all are larger than Cairo)
Anyways, that isn't the point though. You're free to use whatever population figures you want, as it is your scenario. I'm just trying to help, since I'm sure you want your scenario to be accurate with regard to historical figures and what stuff really was in 1941.
My recommendations still stand for the north africa cities.