How to fix "Your system has run out of application memory"

The most common reason for this is your system drive being almost full.

There is also the possibility that an application has a memory leak.

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I had not seen this in a while:

    [Running] com.mackeeper.MacKeeper.plugin.AntiTheft.daemon.plist (KROMTECH ALLIANCE CORP. - installed 2018-12-28)

        Executable: /Library/Application Support/MacKeeper/MacKeeperATd

This is nasty.

You should completely uninstall this.

Your mac does not need any application to "clean", "optimize" or "speed up". They are all scams, and this one is infamous for its scaremunger tactics and aggressive marketing. It is, for all intents and purposes, malware.

Just to say, I concur with @Luis Sequeira1 assessment

Use the Activity Monitor application and make sure to use View >> View All Processes 

What process or processes are using the Most CPU  and Memory.

Often times - the issue maybe not a single Process  alone but a combination of Processes

Also, when the computer is using so much CPU / Memory - it can be a indicator of a Lack Of Empty Spaces on the Drive.

In which case, the CPU and Memory usage would become much more because it is searching for Empty Space to save all the Changes the user is performing.

Also, it depends on the number of  Open Tabs in your Browser, they can also affect CPU / Memory Usage.

Also: the WD software appears to be crashing. There is no need for third party drive vendor software, anyway, and they tend to cause trouble. Your mac can perfectly use the drives without that software.

And you have some very old stuff like Silverlight. It is not used anymore, and has not been in years.

With this old stuff, and the bad mackeeper, if the issues persist even after uninstalling it, it's probably time to make a full backup and then erase and install a fresh system. If you decide to do that, take care to then only migrate the user accounts from the backup. You don't want to put everything back, or you'd be back to where you started.