Sounds like we had a similar situation, so maybe my solution will help you. I finally called Apple support and they walked me through a bunch of steps including going into library and clearing caches and saved applications state. Turns out Malwarebytes wasn't allowed to completely install so that was the problem. My computer works great after the call with Apple support, including Malwarebytes. The support guy I worked with told me Malwarebytes is what they recommend for use on Macs. I'd say give Apple support a call, I was surprised how helpful they were and what they had me do worked for me. Hope this helps.
Good luck.