Just my 2 cents:
1- you could either take a look at Textpattern (this is just a personal preference, but when I already have the html and css design I find easier to port it to Txp rather than Wordpress)
2- or you could consider using a static site generator, such as Jeckyll, Hugo, Pelican just to name a few
If all you've got on your hands is time, I'd suggest looking at creating this using Textpattern:
Between its tag system, and custom categories / post types, you should be able to massage the information architecture you're looking for into the layout of your choice.
Be prepared for a bit of a learning curve, however, especially if you've never tried anything of this scale before.
Grab your self Notepad++, even if your going with a CMS you'll still need to edit files. And, I would recommend not attempting to create your own CMS. Go with something like TextPattern, or as ngilahlekile suggests, WordPress.
While Wordpress is indeed a CMS, it is geared towards blogs. If you want something that's simple to set up with your own HTML templates, try Textpattern. If you want something a bit more powerful, look into Concrete 5. In any case, be sure to read the documentation and expect to dabble in a bit of code.
I hate Wordpress, haven't played with Joomla/Drupal much, but I like Textpattern. It has a reasonable built-in scripting language, so you very rarely need to spray PHP code everywhere.
Textpattern is a PHP-based CMS with an easy-to-use admin panel. It's not quite WYSWYG, but it uses Textile (similar to Markdown) to parse mostly-plain-text into HTML and you can preview the HTML output before going live.
Having worked with a bunch of Web CMSs it's pretty clear that no single CMS will be all encompassing out of the box. Selecting one that fits the purpose well really depends on the usage. So my list of favorites gets tweaked all the time.
I'll start my rant with Textpattern:
Best
Worst
Place holder for opinions on other CMSs