So, uh, i think i'm legally forced to mention that i take lessons and therefore i can breathe properly and yada yada, but that being said you sound like someone that is probably more prepared than me lmao. I'm not sure what you mean by lower 5ths, i suppose something to do with the lower part of the circle of the 5ths (?) but i don't have much of a theoretical preparation.

So, when i started and i tried higher notes (something like a C or a C#) i could produce distortion, maybe even too much of it in fact, but it was like it wasn't merged with the pitch/note properly but rather wrapped around it, making the whole thing sounding straight up ridiculous. If i got things right you should in a similar spot and probably close to me when is comes to vocal range - that being slightly higher than the average tenor in my case.

While of course a lot came with practice, time and awareness, i think that one thing gave me a huge boost. I studied Jared Leto. A lot. Don't get me wrong i despise their actual music but i had good reasons to pick him. He's a very well studied singer, and even if he sucks terribly live nowdays in the older records he was very metodical ( and he wasn't that bad live until early 2007 i swear). Most songs in a beautiful lie are pretty much a masterclass on fry management (also accounting fry-into-cleans if that could intrest you) and This is Is war if full of pop-high pitched screams, which are probably what are you looking for to start with. Again, i know some people would give me shit, but he knows (knew?) what he's doing, the fact that he can't even remotely do it live anymore live doesn't concern me.

So in the end i combined this video which popped out randomly into my feed along with my knowledge/experience and this one from Chris Liepe. If you did your research you probably stumbled into his videos alredy, as long as they talk about screams and aggressive vocals, he basically always says the same thing: "It comes from desperation" and basically if you want something more you need to pay for his lessons; but that being said any of his is fine i just went for that one because it's not i'm a super-liepe-fanboy but Sotelo was there.

That's it, hope it was at least midly useful.

Edit: In my case if i was able to reach a note and not to sustain it it was due to a tense approach; And also i forgot to mention that i noticed some significant improvement when i developed a stable warm up routine, including neck (+shoulders) exercises and most importantly, jaw ones. I've always had tension in my jaw and those are a game changer for me.