So, I edited some settings on the forum since it's back.
First I activated something called GZip page compression : Do you want to compress pages in GZip format when they are sent to the browser? This means quicker downloads for your visitors, and less traffic usage for you. I put it at max compression level too so it should help.
Then I set up a *NIX load limiting : Limit the maximum server load before MyBB rejects people. 0 for none. Recommended limit is 5.0. I put it at 5.0 like they recommend so we'll see how it does. That way if server usage becomes too important I think it will just block the forum to some people, so we won't probably reach the CPU limit usage again... hopefully.
Finally, I disabled the forum jump menu that you can see at the end of every page when navigating through the forum.The forum jump menu is shown on the forum and thread view pages. It can add significant load to your forums if you have a large amount of forums. Set to 'No' to disable it. I think this could also help since we have a lot of forums and subforums.
To go with that I put back the flood check on the chat at 30 seconds. If it crashes again though I will raise it again. Also, I only allowed registered members to see the chat. That way people who just come on the site and don't register won't send tons of requests to the server since you'll have to be logged in to see it.
If Caps does make his way over here, I'll be on until around 12:30 or so to see if his power's working again. If not, I'll be up to watch the junior game tomorrow so pretty much any time after that to like 7:00 I'll be available
Site back again. I didn't disable the chat, but I emptied the table instead so all the messages have been cleared up. Raised the flood check to 60s too. I think if it still doesn't work after that I'll disable it completely or try something a bit weird, as in using a database from another host for this one... But I doubt I have the PHP knowledge for doing that.
Or we could just find a chat website, or open a IRC channel for our league, but that would mean everyone would need to install a IRC client. :p
Alternative chat page if ever the official site is down or not accessible for you. At least, you can still get the latest announcements and discuss with the others. The chat is the same as the one on the official website.