I have a custom Visual Force page, but it always there is a padding around the VF page that is quite noticeable in the Lightning experience. Note the white area around the VF page in the attached screenshot. It seems like a standard setting in lightning to have such padding for a visual force page. Is there a way to remove/overwrite this padding please?

I need to make a scrollable area to spread to the end of the page, so want to pass the inner height of the window to a CSS variable. I see from the document that the only way we can manipulate CSS in javascript is to add and remove class.So wondering if it is possible to pass a parameter from javascript to a CSS variable? 

I need to implement a scrollable data table in my current project. The way I am doing it right now is to create two tables, one only contains header, and the other one only contains body.But this methods brings in problem with alignment. I see that in lightning standard page, there are scrollable tables, so wanna ask is there a standard way doing this that won't bring about any problems?