the scroll is working normally. When the slider is touched on a mobile device, the browser is expecting you to swipe the slider images so the page scrolling stops.
the HTML widget plugin provides integration of 3rd party content via widget zones, it doesn't deal with layout formatting or elements positioning. In order to achieve your desired layout you have to be familiar with css.
can you please start a support ticket and preferably provide us with login credentials so we can log in and inspect what the problem is?
the category image dimensions are determined by the corresponding setting on the "media settings" page in your administration. When a setting is changed there it is also necessary to clear the cache from the admin panel otherwise the new setting will not be applied on the website (as the images are all cached).
If you have a persisting problem with image dimensions please open a support ticket at nop-templates.com