Hi there,
1. so do you want the background of the Heading to be in white and extend the fill width of the screen? If so you can do this by editing the header element and giving it a background color and maybe some bottom padding.
We can then provide some CSS to remove the space between header element and content. Let me know if thats what you require.
2. So Edit the post you want to Stick to the top, and in the Status and Visibility settings check: Stick to the top of the blog / front page