Unwanted space between hdri and environment?

Hi,

How do I remove the space between my hdri background image and the environment, although not easy to see as the wall is white but there’s some space between the mountain and the wall that’s white, I’ve tried moving the skysphere down it does nothing?

I’m also trying to remove the paralax in the background image so it it doesn’t get bigger or smaller (doesn’t scale) regardless of how close to the white wall you are or not?

I thought i had this cracked but clearly not, would appreciate some help.

SpaceHdri.jpg