I'm sorry about your frustrations!
I think most of us get them, and they are a pain.
I understand what you mean about hair not being silky. I have a bumpier texture. It's never silky the way that fine hair feels silky. I just have a coarser hair texture, so there isn't a whole heck of a lot I can do with that. Frizz is a common companion. For me, air drying leaves me frizzy, yet with less volume than diffusing. If I am patient with my diffusing, I have less frizz. If I am in a hurry, more frizz. I like plopping, but not everyone does.
Maybe you just have a naturally coarser texture.
I've not run into much cone overload, so I can't help you much there. I had it a couple of times, and it just felt like there was a layer of something on my hair. Stuff would come off if I rubbed my hair between my fingers. I'd get this with dimethicone and amodimethicone. Some people tolerate it better.
I can describe what protein buildup feels like on me, but I'm not sure if it will help you. In a stronger form, my hair feels like straw or dry summer grass. I'll get this from wheat. From other types of protein, my hair will feel brassy (like blonde dye gone wrong), have a dry coaty feel that I just can't explain, or will be much more difficult to comb. It feels like I really have to pull hard and it sort of feels like my individual hairs are sticking the the teeth of the comb. It also just doesn't feel as conditioned as it would without a protein buildup.
I do use Low-Poo once a week as it seems that even tiny amounts of protein bother me now. It really gets on my nerves.
You may well need a thicker conditioner, although it doesn't seem like you're having super cold winter weather. You could do a trial of something thicker.
Also, for my texture, I have found that things with glycerin realy helped out with the feel of my hair. It was the closest thing I've had to silky.
Med/Coarse, porous curly.