I would disagree on the 400m ability as of today.
Let's forget block starts, it's anybody guess how the 800m guys respond to those, in an all-out flying 400, Hoey is in the mid to high 46's. Brazier ran 46.1 indoors before his body imploded (so maybe 45 mid potential outdoors) - but that was 2022 and well all know how long he was out.
He's doing what he's doing now off just a natural improvement in strength throughout his twenties (that we all have irrespective of running or not), a much better training philosophy and execution (Peter Julian, not so good) and the little things that help older guys (softer spikes for training), bi-carb etc etc. He's not a 45 point 400m runner anymore. So to say he's significantly better? That is a hot take because it's underestimating Hoeys ability to get round a lap and overestimating Braziers. I think if those guys lined up in a TT together they are probably neck and neck and who ever "wins" it is the guy who feels better on the day or who cares more about it.
As for the 600m record, this has been talked about a lot, but the volume of guys contending at the level maybe just below the record is actually hurting the chances of it falling, not helping. To run these times (and I think this is the case with the 800m outdoor record too btw), you can't really have a race anymore, it has to be a solo TT effort similar to the way Hoey just ran that performance. So over a distance where 4 guys can all get out at the same speed and especially indoors where you need to establish that position on the track, it's not really that conducive to optimal times. The chances of that record going down in this NB meet I don't think are high, but that's just my opinion.
Regarding top 3 in US - Hoey has a chance? Did you mean at the national champs or just ranking wise? He was the US number one last year performance wise (and not just a one-off, he was consistently the fastest US runner across the season). But if we are attaching his prospects to the concept he may just totally implode under the "zero-rest, always-on, 110% all day every day", then we also need to say Bryce Hoppel is probably beginning the natural descent of his career arc at age 28, yes Brazier has missed a ton of time that will add on to his clock but he still is 29 in April so everyone has their extenuating circumstances.
I feel like Hoey will get through the majority of the outdoor season before the stress breaks him (which I agree with you there is a really solid chance it does). But I also think it's going to yield a performance at least as good as last season if not better - something in the high 1.41's