Q: Yahoo website is causing MBP to crash

That looks like nothing I would expect in that there are a tremendous number of open files and ports, but it is consistent with the problems you're describing.

Open System Preferences > Network. Choose the network interface you are using when you have the problem (probably Wi-Fi), then click Advanced...

Click the TCP/IP tab. What does it say next to "Configure IPv6"?

Try changing it to "off". After making that selection, you have to click OK and then Apply. Restart your Mac and evaluate how Yahoo's website performs.

Sorry, I meant to write "Link-local only". Try that.

OK, revert the change by setting IPv6 back to "Automatic".

Something isn't adding up, which usually means I'm missing something obvious. I observed a very similar, if not identical problem a few days ago but the wireless network I was using was performing a bit slow. After loading some web pages (none of them Yahoo though) "Safari can't connect to server" appeared and no more webpages would load until I restarted the Mac. That is what led me to suspect network problems. I was unable to correlate it with anything specific, and the problem went away on its own after connecting to a different network with better throughput. It shouldn't occur at all though, even on a slow network.

Confirm you are not using any third party "memory cleaning" applications or any similarly categorized utility. It would certainly cause what you're describing.

Another suggestion: Enable Safari's Develop menu by opening Safari's Preferences... Advanced, and select the box "Show Develop menu in menu bar". The Develop menu will appear. When the problem occurs, select "Empty Caches". Determine if that has any effect.

To isolate the potential problems to your User Account, please create a new, temporary User Account according to the following: How to test an issue in another user account on your Mac - Apple Support. Reply with your observations using the temporary User account. If the problem does not occur while using it, some more suggestions will be applicable.

When you are finished troubleshooting, you can delete that account.

I realize this is getting old and it seems no progress is being made, but everything you are doing will eventually isolate the cause. It may or may not be anything you can fix though.

Next, try the following:

1. Shut down your Mac.
2. Load OS X Recovery by holding ⌘ and r (two fingers) while you start your Mac with a third finger.
3. At the Mac OS X Utilities screen, release those two fingers.
4. Choose Get Help Online.
5. Safari will launch, but it will lack your bookmarks, favorites, history and other preferences.
6. Load a few web pages and observe how well Safari performs in Recovery mode, compared to how it has been.

Restart your Mac normally and describe your results.

Thanks. In the same manner as finding the Internet Plug-Ins folder contents as described in Apple's Support document above, please post the contents of each of the following folders. In other words choose the Finder's Go menu > Go to Folder.

In that field, type

/Library/LaunchAgents

and click Go. Post the contents of that window. Be sure to capture all its contents. If you are using "list view" please expand the Name column so that the entire file name is readable.

Repeat the above with the following

/Library/LaunchDaemons

and (though it should already have been ruled out as a factor)

~/Library/LaunchAgents

Post the contents of those three windows.

It appears something called K9 Web Protection is installed, or was installed at one time:

http://www1.k9webprotection.com/

Same goes for "CleanMyMac". Any system that has been affected by it will not work properly.

Try uninstalling "K9 Web Protection" first, but if that is not successful the only certain remedy for CleanMyMac's effects on a Mac is a complete system erase and reinstall.