Thats alot of post from so few members. While you may not have many members, at least more than half are active and going by the number of posts and the time the board has been open you have done very well.
As for the server load, it depends on the other sites that share the server, its quite posible that its not your site generating a higher than normal load, or that the server specs a low.
Assuming that the majority of the posts have "real" content and are not just SPAM or other useless posts then its all good IMO, otherwise it could put members off thinking its just a site with a bunch of people posting mindless rubish, you'll be the best one to judge this