change your capital, and put it at the centre of your empire.

if that's not enough, then put the taxes to max, draw out your army, let it revolt and exterminate the population when you take the city back.

Now as the julii you have access to good temple to keep public order.
build temple of bacchus in the cities where you know you'll never leave a governor in.
build temple of jupiter in the cities where you can build mines to reduce corruption., and in every city where you don't know what temple to build.