merry fable
I don't know how to use DPL so I can't advise on that
you can use the parser report to determine how many times the template's been transcluded but I don't think it would be able to find how many of them have a parameter filled in.
You could also probably use Lua to transclude the page and look through the raw wikitext. If you have really complex needs you can use [[w:Module:WikitextParser]] to get a list of all templates and find the parameters
Anyway it would probably help if you described exactly why you need to count how many times a parameter is used
muted robin
lunar finch