Does the presence of a dipole moment in a molecule tend to increase or decrease the strength of intermolecular interactions?

Yes, the presence of a dipole moment in a molecule tend to increase the strength of inter-molecular interactions.

Explanation:

Dipole moment:

It is a vector quantity and is used to measure the  distance between the two opposite charges.

what experimental evidence led scientists to change from the previous model to this one?

a few of the positive particles aimed at a gold foil seemed to bounce back.

the colors of light emitted from heated atoms had very specific energies.

experiments with water vapor showed that elements combine in specific proportions.

cathode rays were bent in the same way whenever a magnet was brought near them.