Thanks all! I tried BetterBear's point 3)
Despite putting the commercials next door to the industrial zones, it doesn't look good:
With houses:
Regarding the other points:
1) Won't that affect how the zones evolve?
2) In reality, it feels like a buzy intersection without traffic would preform worse. When should traffic lights be used in the game?
3) Didn't turn out that easy.
4) Like having double roads, one way directed roads in each direction? IMHO it feels like theotown would do good with one size bigger roads than country road, but not as large as avenues.
5) I probably restart, it wasn't a big city.
6) Maybe the settings on easy level (that I'm playing on) should have better traffice percentage by default