Hopefully I'll get a chance in the next couple of days to possibly put a lid on this thing. I just realized I have some of these on hand:
https://html.alldatasheet.com/html-p.../1/SS8550.html
They appear to be a close enough match to the 2SA812-M6 PNP in this application.
If I can get it working right, I can imagine the 4172 will work better than it ever has for me, even with sub-optimal terminators.