To clean the bores those pins slide in ,you might use a cloth wrapped around a screwdriver and really get all the unwanted stuff out of there.
There is a special caliper pin grease that has a high melting point ,is not harmful to the rubber boots and that should be used to lube them on assembly.
That area is subject to all kinds of road grit and cleanliness does pay off in the long run.

 

Worse still I think I may have tightened that bolt too much

 

I would not think that could cause any problem , but some of those pins have an indexing position that must be applied and we don't know if that even applies here without looking.