1. To reduce the gap between the slider and the content you'll have to paste in this custom css code inside the dedicated area for  Custom CSS Code under the Theme Options Panel:

.page-id-7 .rev {   
   margin-bottom:50px !important;

The code above will reduce the default (100px) bottom margin of the slider in the page with the id 7... Find your page id and replace "7" with your id.

On your other pages please use  blank dividers with negative margins as they should definitely work

2. To reduce all the blank space before the footer use this code:

.wrapper {    
   padding-bottom:0 !important;