To fix the button problem is easy, just open client.cs and at the end of the file add Your_Button_Name.text = ""; and there will be no text on the button.
As for the missing skybox, there is no way to fix it that I know of. The player must have the sky files in order to see it properly. However, if you ask players to re-join while your sky is active then they will probably download it.
Everything else you have done seems to be fine though, if you have any other questions then just pm me.