Looking to know what more security work can be done to this basic website -- 2

So far we have done the things marked as complete on this list. There are also a few things marked incomplete. I need to know what else can be done regarding security. I am looking for a list of things that can be proposed on top of the things in this list: The task is to give me that new list of items, ideally another 10+ security related items, with a short description. Should not take someone who knows what they are doing more than 20 minutes. This will lead into the work needing to be completed. It is a basic HTMP/PHP website, no wordpress, hosted at sitegroung via dyn dns. There are no databases used.