The old pricing is never coming back, just to be clear. However, if you bought the one time (lifetime) license at $97, you still have lifetime access to the original version of the software you bought. However, if you want the new/upgraded features (like KC scores), you need to buy into a new plan. If you still have questions, contact me or Long tail pro support at longtailpro com / support
Use the Keyword Planner to flag any terms on your list that have way too little (or way too much) search volume, and don't help you maintain a healthy mix like we talked about above. But before you delete anything, check out their trend history and projections in Google Trends. You can see whether, say, some low-volume terms might actually be something you should invest in now -- and reap the benefits for later.
Long Tail Pro is a keyword research tool that helps you quickly find low competition keywords for your website. In particular, the tool is built for people doing SEO (search engine optimization) as opposed to people doing paid ads (Google Adwords PPC). I'm sure there are some advertisers that use the tool for paid ad keyword research, but the tool was built for SEO keyword research.