Your computer is having Kernel Panics which is what your EtreCheck report stated, see below:
"Anything that appears on this list needs immediate attention.
Kernel panics - This system has experienced kernel panics. This could be a sign of hardware failure."
KP's can be tough to diagnose as they can be caused by either hardware or software. Common hardware causes are RAM related and failing HD's. My guess is you may have upgraded the RAM yourself. If that guess is correct, if you used anything other than either Crucial RAM or www.macsales.com RAM than you may have a RAM issue. To diagnose if it is RAM, please remove all the upgraded RAM and install the original RAM that Apple installed when the compute was originally sold. If the KP's disappear then you know it's the upgraded RAM.
To test if the problem is related to the HD, you should download the free version of DriveDX and test both the HD and your SSD portion of your Fusion Drive. If ANY errors appear that confirms the HD is causing your KPs and needs to be replaced!
While at it you should test all external HD's too with DriveDX as they can also cause KPs.
As for software causes, the BEST method to test for those is to ensure all third party apps are 100% up-to-date! You may have older versions that are simply not optimized for the version of Mac OS installed on your computer.
Best of luck, you have some work ahead of you.