Okay, I have a status.
I went ahead and restarted my old subscription for Object Desktop, then I downloaded and installed OD. Then I grabbed the new versions of Fences, Windowblinds, and Start 11. Yeah, for this machine I still like the old start menu motif and layout.
With Windowblinds installed, I looked and looked, but couldn't find anything that would increase the text sizes.
However! I may have stumbled upon something helpful.
By poking and poking and poking around, I came upon a new setting for text size. Well, it's new to me:
Windows Settings/Accessibility/Text Size <-- This is a slider. When I found it, it was set to 157%, but the font sizes were very small for that to be correct on my system. So I grabbed the slider and moved it (yes) smaller...down to 150%. And guess what, the font sizes GOT BIGGER in several places, such as my Firefox tabs (the text on the tabs themselves, not necessarily the text on the pages represented by the tabs), a couple of open Windows File Explorer instances, plus an XYPlorer instance that I had also had open. And the text showing up on my Windows settings dialog box too.
I opened Affinity Photo 2 and went into the help dialog, which I know is too small from before. No improvement there, so this is still a struggle.
It's unfortunate that Windowblinds doesn't let me change any UI font sizes, but there seems to be SOME improvement from the accessibility change I made. I'll need to use it for some days to see if it really will be workable. And at least in Affinity Photo, it doesn't help at all.
Other issues (and maybe more) remain.
1. When using Firefox to access a YouTube live-stream, there's an ad that pushes the chat window too low in the browser window to be able to type freely without having to zoom-out that window to be able to read the content of the chat. And the amount of zoom-out that's needed is so much that it will make the chat hard to read. So no improvement here either.
I have in the past used Adblock Pro to knock out that ad and make the chat function easier to use with a larger text size, but Google likes to keep hitting me with warnings about how adblockers violate their terms of service.
2. The text beneath my icons as they appear in Fences, now underlap the icon below. It's minor, but still annoying.
3. I can't find either skin file (.uis and .sss) anywhere, so I don't know how I could make that adjustment noted above by Gaspershooters. I'll keep looking.
So the TLDR is that I have some minor improvement, but more work is needed.