First, remember that clearing the creek is part of the "building" class. So they are doing what you are telling them to.

Second, has construction of the hut been started? You are only able to build huts when your population gets to a certain amount. So if your population is not over the required level for your next hut, you are not able to build it.

As to your second question, it seems to be like real life. You can get 6 boys (or girls) in a roll before you get a girl, or sometimes you'll get nothing but girls for awhile, but most of the time it averages out.