I have been ranking national in a Non US market similarly. In total their are 8800 impresssions in total in my Places account but a very low action rate similar to yours.
The reasons for this can be that they are generic keywords showing on local results. So, mostly people who take any action on these kinds of listings are probably searching uniquely for local combinations of similar keywords.
I was surprised to see that the niche that I targeted was having one box listings, 3 box listings (all mine) and a combination of so many local and national combinations showing my Places Listing. But, still not much activity apart from people directly calling after looking at the Places listing.
