Hi,
It is unfortunately not possible to add a scrollbar to the isotopic results list, there is only a pagination option for it. By default the browser scrollbar would display, but you have the search in a fixed position container, and fixed elements does not trigger the browser scroll. This would only work, if you had the results somewhere within the page content, outside of that fixed container.
Currently there is no search history, however we are working on a feature for a future release for better statistics. That will include all of this information 🙂