no sidebar on homepage & category / hardcrop thumbnails

1 – on my blog page http://www.denieuwe30er.nl/category/blog/ I have selected 4 columns, also a widget in the sidebar. Only 3 columns are visible and no sidebar, if I would have selected 4 columns with no sidebar, 4 columns should be visible. The side bar does appear on the individual blog posts. Widgets are in Sidebar Top. Widget is selected to be on Homepage and other selected pages (plugin Display Widgets).
My blog overview page is a seperate category btw (to prevent sliders showing up here).

2 – on the homepage I selected a static page. Now I cannot find anything on this, but maybe the sidebar cannot be combined with a static page. I put widgets in it, but nothing is visible here either.

What goes wrong here? Thank you…