A basic upgrade increases farm profits by a fairly small amount in my experience. However the population grows to, which also increases taxes (& probably trade). Your 0.5% growth rate in Patavium, matches what I've seen, it stabilises without revolution for Julii.

But these large town issues, may be more of a problem for barbarian factions, which have fewer "civilisation" options to reduce unrest.

Loss of revenue due to a rebellion, appears less important to me, when you have a very large number of provinces, so struggle to understand why so many guide posters have been so single minded to avoid it.