I'd be interested in the whole process you did to do a "Full Uninstall Instructions". I've done a process of uninstalling everything roxio related from some pretty specific guidance I googled. Probably half of the items that it said to remove I couldn't find on my system. I still can't get Toast 17 to open, with a similar crash error to what you posted.
If you can post those instructions I would be eternally grateful.
I'm going to see if it will install on my 2017 MacBook Pro which I don't think I've ever had any version of Toast installed on, and see it works on that system which is the same OS as my MacPro tower.