Is there an example of a FPTP parliamentary system where there are many small parties? Or is the proliferation of minority parties entirely the result of the PR system?

If there are no obvious counterexamples, I might argue that an advantage of the few-parties-FPTP system is that the party platform is made public in advance of the election, so voters know what they are voting for. In contrast, in the many-partis-FP system the coalition is not decided until after the election, so you don't know what you're voting for.

A current example would be if the German Greens were to join a coalition with the CDU on the right. Would Green voters have gone for the CDU if they didn't have the Green option? Or are they a more natural SPD partner...