Removing main content block on frontpage
Sorry, but that's not the way to do it.

Instead of creating a block display in Views, create a page display. Choose a path for your views page, for instance "home", and save the view. Next you go to /admin/config/system/site-information and change the value for 'Default front page' (it probably says "node" now) to the path you chose for your view ("home").

When you follow this approach, the main content on your front page will be the view.