It's hard for any new site to get visitors. Don't get discouraged. With a new directory, you should be seeding the categories a bit to get things going and entice the bots to visit more frequently. Just maintain strong editorial controls and create something worth visiting and you should be fine.
Not really, those websites usually have a low DA and few backlinks, for sure will bring almost no value for your website, so it doesn't worth the effort doing to do that. Go for high pr or high DA domains, as you may or may not know the pagerank is updated slowly, around every 3-4 months.
If that directory is having PR 0 doesn't mean it's spam but the point is it's having low PR then may be it will take long time to crawl...