Seatpost won't let me set my saddle "level"
Unfortunately, this is a common issue with more basic seat posts. 

There are 2 options:


Use sandpaper or a Dremel to remove the teeth which fix the angles of the seat post. If you make it completely smooth, then you can use grip tape like that designed for a skateboard deck to add friction without locking you in to specific angles. This approach has drawbacks. The grip tape may need to be replaced on occasion. You need to be careful not to remove too much material from the post, as it risks breaking the post in use. As you can imagine, that would be painful. 
Replace the seat post with something without that limitation. 


I hope that helps.