Txurce
Deity
Our first hypothesis is that its a "big city, many city" problem. Your play results support that. Crdvis is providing a counterpoint from his own play. That may suggest the problem is more specific. We need to hear all of these viewpoints in order to understand what problems exist.
I also sense that the non-spiral unhappiness issue some players have is specific to a certain playstyle. It's also relative. My happiness isssues are no longer hugely problematic, but they are night and day from players who have no idea what I'm talking about. If I have 10-12 cities, am average to high in pop, average in SPs, high in tech, build essentially all "helpful" buildings, usually lead in Wonders, and adjust city workers and specialists when needed... something else is going on.
Not enough TP's? TR's all in the capital? These seem to point to poverty more than distress, but distress is my #1 unhappiness driver.