Aside from the population already mentioned, the biggest thing that caught my eye was the salary. Based on various class population, tax rates, etc, the starting and monthly incomes seems skewed for the upper class. living paycheck to paycheck is understandable for lower class, half and half for middle class but not for upper. They will have a savings, inheritances, etc. If you consider starting vs monthly, it's 7d, 8d, 9d vs 2d, 4d, 6d respectively. I guess I just don't understand the logic behind that. A king is likely to have a treasury worth at least several times what they make in a month, not 1.5. A Duke isn't likely to make 2/3s what a king makes, nor a Marquess making 1/3. In my opinion, the differences in wealth should be much steeper, not to mention much higher. The king of a country in a world with that population density, averaged out for 9 kingdoms, will make 59,139,892.16666667 gp per week in taxes off just 20% of the population that is lower middle class.
Formula used to figure this is 3,225,812,300(population total)/9(number of kingdoms)*.2(20% of pop)*11(average of 2d10)*.15(tax rate)/2(based on kings making as much as lower and middle upper class combined).
Obviously there are expenses, but even with a profit of .1%, that's still 59k a week.

Anyway, good luck with your realm and I hope it works out.