Hi Slon

I've now managed to complete a campaign as Scipii on Medium/Medium and have now moved up to Hard/Hard. The 2 areas I see as the root of your problem are your current population levels and your enslaving policy when you take over towns. Once you reach the 24,000 population level that gives you your final level buildings you really don't want your population to go much further than that. I would move a large army near a city with 40,000 population, move the garrison out, and set taxes to the highest level. This should cause a revolt and you should then retake the city and exterminate the population. This will reduce the population to a manageable level and give you revenue from the extermination. Once retaken the lower level population will be much happier and you can manage to set the taxes at a higher level.

When taking new settlements enslaving is only adding to your population in your already over-crowded cities. Once you have reduced the populations in the problem cities you may be ok. Alternatively you could just exterminate or occupy when taking new settlements.

As a side note you may want to check that your generals with the highest influence and management skills are in your biggest cities.

Hope this helps