I've reviewed the "todolist" and your website. Easy items 1-4 appear to be simple modifications, although without seeing the code #2 will depend on the cause of the past lookup words not being displayed. The 3 moderate items do not appear to be overly complicated tasks, however again, without seeing the code its hard to say exactly what will be required, and with respect to item 3, it will depend on how far the past programmer got in adding the functionality.
The items listed as hard, while they don't appear to be overly complicated, more information would be needed to determine what needs to be added or modified and of course seeing the code to determine the amount of work. The same goes for the Admin items, I'm sure we can work out better ways of managing the functionality, but without seeing the Admin system or the code its hard to guess at what is needed.
The only comment I would like to make is on banning users by IP address, while it is simple to add you should be aware that it can have unintended consequences. The majority of internet providers have a limited number of IP addresses that all of their customers use, so banning an IP might not block the person from your site and may block others instead.
I have been working with PHP for over 15 years, and I would happy to assist you with your project. If you would like to discuss further, please contact me. My bid is based on 10 hrs work which should cover the majority of work.
Regards,
John