Pre-Modern Astronomy vs Habitable Venus

[sandcastles]

S.M. Stirling has two novels, In the Courts of the Crimson Kings, and The Sky People, in which Mars and Venus resembled the way they were portrayed in pulp fiction. He has a good rationale.
Harry Turtledove involves Mars in several things, and has an alternate Mars in "A World of Difference".

I saw the article about the moon not stabilizing Earth; what would be the situations where a large moon would be needed to stabilize a planet? Would a much larger planet ever experience chaotic changes in its rotation or tilt?