Buddywizard isn't quite working for me yet, it freezes on .Net 4.6.1 - but I did use that info to hunt down the official installer for it, and found out:
"The update corresponding to KB2919355 needs to be installed before you can install this product on Windows 8.1 or Windows Server 2012 R2. "
So, I'm installing that and hopefully that will fix the dependency chain and let this all work. I'll post any further manual intervention I have to take so hopefully the BuddyWizard can be a full troubleshooting tool; if I don't post after this, assume this single download fixed the rest.