I like what you doing, but I am not 100% sure if you are doing this in the correct manner. We should not encourage people to post within a required post count. The interaction should come naturally, like you would be walking around at a party and joining discussions that spark your interest.
The main focus of the merit system, should be to improve the post quality, not the quantity. It also serve as a educational tool for people to see what quality posting looks like.
I would remove the minimum post requirement and just concentrate on highlighting the quality posts that adds value to the forum. ^smile^