Is there a database of pollen-seed distances across plant species?
In my searching I didn't find a comprehensive database of this information. There are biologists interested in analyzing seed dispersal distance as a trait however. 

Vittoz and Enger (2007) used plants with known seed dispersal along with characteristics about these species to predict dispersal distances for other species.

There is another study here that examines the relationship of plant height and seed dispersal. They provide interesting background information as well on the trade-offs associated with a particular dispersal mode. For example,

"It is often assumed that there is a trade-off between maternal provisioning and dispersal capacity, leading small-seeded species to disperse further than large-seeded species."

It is certainly an area of research actively being pursued but there doesn't seem to be a list or database of these dispersal traits by species. There is information on dispersal distance by mode in the appendix of the second link I've provided.