Hello Joe,
I installed the ~700MB windows update stated above that I found was sitting in my Optional Updates, then rebooted. Toolbox launched successfuly, application was usable and responsive as expected and computer did not hung. Seems like that did the trick!
Following my ordinary use case on my pc I unplugged my external USB linked HDD, at which point the computer froze again, exhibiting the exact same behaviour stated in my OP upon Toolbox launch. I had assigned NO specific user-requested processes upon toolbox at that time. Meaning no scans or stuff like that, and I believe there was no apparent activity in my SSD at that point, so probably no background Toolbox processes/services I guess.
Rebooting after that computer freeze (and first ever and only successful launch of Toolbox), behavior resumed to the expected problematic one described in OP:
Computer freezes upon Toolbox launch.
