New Post: Select amount of Hashtags

I use Search.SearchTweets("#hashtag") to look forets containing a specific hashtag.
The problem is: I get only a few newer tweets. Is there a possibility to select also older Hashtags?

Second question:
I want to display how often a hashtag was used.
Is there a possibility to select only the count of all hashtags?
This would be really great if you just want to know how often for example the #facebook hashtag was used. (It does take very long to select all entries. Is there a solution to get only the count?)

Thanks for your help.