Hi, Firefox. Thanks for responding.
This might be lengthy.

My hair is porous and fine or fine/medium. I don't know how it got to this state, just that it happened pretty quickly. I don't swim, use heat or dye, and I'm never in the sun for long periods. All I can come up with is diet.
I used a chelating shampoo where I previously lived (years ago), but it never did anything. Admittedly, I don't know whether I have hard water at my current location, but I see no obvious signs of it.

I'm unsure of the dews here, but when it feels particularly hot and/or muggy, all humectants leave me uncontrollably frizzy and too soft or too dry. Some also leave me tangled/matted in said weather. One possible exception is honey, which I've had mixed results with when used in DC's. I avoid humectants in the winter, also, with the exception of panthenol. Under 'mild' conditions, I seem to tolerate panthenol ok, too.

My current routine is to just do a rinse with Mill Creek Biotin. I switched to a coney protein conditioner, Organix Biotin/Collagen (***I do not use cones; this was just a brief experiment***), when it started getting muggier outside but stopped when I noticed more shedding (I think it may have been the particular Cyclo-cone in it).
I don't use leave-in right now. I didn't fare too well last summer and the one before that when I used leave-ins (I alternated between Giovanni SAS, KCKT, and Trader Joe's Nourish Spa). I also don't really DC much anymore, but for years my go-to was Giovanni SAS. Over time I grew leery of it because it always left me with super soft but completely dead curls that were crispy by morning. I've tried several other DC's (Aubrey O Honeysuckle, Kenra, etc.) with no consistent results.

The leave-ins I've tried in the past several months include:
Darcy's Pumpkin Seed, Camille Rose Naturals, Oyin Hair Dew, Giovanni Smooth as Silk and Direct Leave-in. All leave me soft, stringy, frizzed, waxy/mushy and brittle. The SAS is the 'least' offensive but still terrible.

Yes, that's the Komaza formula I used yesterday. When I wet my hair today, it felt soft and pretty manageable, but the roots were stuck together as though my cuticle had been raised.
What I meant was that when I styled after the treatment, my hair was so soft I could barely feel it between my fingers. I rinsed later on and my hair felt like it could just fall out - It had no strength, no real 'substance' to it, just felt very soft. I did use coney conditioners after those first two treatments, so I'm wondering whether that had anything to do with it.

I've not tried coconut oil.

Hope this helps any.