Several points to unpick here.
First up, the app's manual (Help). It really isn't a conspiracy against users. The v6 UI contains views/data used in v5 but is a complete re-write, plus it is still evolving and ironing out kinks. It is written primarily by the developer (who is writing code otherwise) and the two main volunteer contributors are currently busy in other things. As one of the latter, I'm doing a full time MSc - indeed I'm writing this as a break from writing up my dissertation; less free time. I'd agree the manual lacks an article on the tear-off concept. It's much harder to write a manual when the subject matter is still evolving build-by-build. Plus one has to balance the users who get angry that there's 'too much to read' in the manual against those similarly angry 'everything isn't explained'. There's a similar turf war between those who want in-app help and those who insist it must be a form of 'paper' (i.e. PDF) book**; no one's ever happy.
Tough gig, writing a manual for a multi-facted tool. Although TB's now 14 years old, v6 is in many ways a 1 year-old but as complex as the v5 that had 13 years to ease into current form. So, could the manual be better right now? Yes. Is it laziness? No, and the manual is being worked on. v6.1.0's Help (manual) added new content - not just release notes.
** TB Help is written, like v5 in a TBX. After my course I hope to be able to build into the new help TBX the structure I devised for making a PDF that I did for the v5 file. But the open source tools have changed, etc., so it's another not-simple thing. Same goes for aTbRef6; the current one took 9 years to write and again i'm starting from scratch. These things take time.
Tear-off windows. Off the top of my head two pop-overs, Get Info and Search (Find) results, can be 'torn' off; there may be others. By this I mean if you click on the pop-over (but not on a control or input thereon) and drag, the pop-over alters to become a stand-alone window. It is tied to the original source note / search made; with find, I believe you can run still run a new search from the tear off, plus the drop-down in the search box lists recent searches- click one to re-use it. The window persists until closed or the TBX is next closed. You can try tearing off other pop-overs - they either will or they won't.
$Text also has a sort of 'tear-off'. Select a note, View -> Text window (Cmd+Opt+X) and that note's $Text are shown as a separate window; from v6.1.0 this also includes the notes key attributes (KA) table - great! These separate text windows only last for the session (I think!). This area of extra text window is evolving, not least as it get TB6 back into the scheduling problems v5 had in trying to keep all windows in synch and updated (i.e. annoying for the user but really hard stuff for the developer). A known issue is $Text scrolling to start or end and losing the insertion point, but it's work-in-progress.
"Tinderbox is not my typing machine". I very agree. I'm in the same camp but for many other users TB is their primary typing machine (output/word processor). It the latter for whom much of the new RTF improvements were added (plus the new frameworks offer support for them). It is a big headache for the developer of a toolbox like TB as groups of users make heavy use of small parts of the app and resent work done on other aspects of it which appear as wasteful for their own use perspective.
Search is indeed vital. The move to a (primarily) one-window app reflects changes in the Mac environment and the advent of a more mobile on-everywhere expectation of users (or in broadband connected parts of the world!). I too found TB in the same way. I can't point to a strategy but I've managed to adapt to v6; there was a period of pain but now the benefits (many) outweigh the comfort a complex UI I knew well. It does seem some sort of a return for the history view (or the queue of notes visited) might be a good thing to add back.
Self-taught? Me too! Never had a day's formal computer/app training in my life. I help here as it returns the kindness of strangers I get elsewhere online. You are not alone. I learn by simply by not being too embarrassed to ask if I don't know stuff when all around seem to.
The point about the general concept of online 'user-to-user' forums are they are
not formal tech support and if vendor staff participate, they are doing so
as fellow users. The lines can blur, but the point is that complaints to the vendor should go to the vendor, otherwise complaining posts are simply blaming fellow users who can't alter the design and thus can't help; plus everyone gets a little unsettled and new users get disheartened.
So, here it's better to frame a question differently. "Search sucks, I can't do X like I used to…" which basically says the design is wrong. But, "I'm used to doing X via search is this way, but I don't know how this is now done". this lets users either point out the replacement method, a workaround if no direct replacement or a suggestion that you make a feature to the vendor for a closer replacement for your old workflow. That way the user-to-user model can do the best for all involved.
I do get that changes have left you annoyed, I get days like that too! Still, I hope the above has helped explain it's not a conspiracy.

As ever, if stuck, ask a question. now, back to dissertation writing/beta testing TB (bold or foolish choice to combine the two?).