Mindspark got deleted unexpectantly a few weeks after having asked Thomas Reed at Malewarebytes Support to look into my problem. Treed was not able to identify what was preventing Malewarebytes Premium from removing Mindspark. He speculated that my consecutive use of Disk Utility SOS, my frequent restarting of this Mac or something else must have been the drigger that allowed Makewarebytes to delete Mindspark. A disk corruption is a possible cause.
Another thing I must mention: I also deleted the free version of Malewarebytes I still had in my applications folder. Thomas felt it could have been possible its history had been corrupted. And surprisingly, even Bitdefender Premium didn't detect Mindspark. You may want to try the free AVG Antivirus, il seems to be able to pick up a lot of bad stuff other antivirus are not able to. Finally, if you do not have one, add a good VPN App in order to switch server so the malware will not find your previous Mac IP address.
I do not have further info. I consider myself lucky I got rid of Mindspark. Try all these possibilities, you may be successful.