Thank you for the welcome and advice!
As far as food preferences, it only eats seeds and bread (which I have now read is actually ok in moderation if it is whole wheat). I have pellets in there but it hasn't tried any yet. I've offered it a few veggies that it hasn't touched and I had to take out. I got some treats that are basically bits of fruit rolled in seeds and put some of those with its food in hopes that it would be "tricked" into eating something different. I found one at the bottom of the cage later on. It looked like that cockatiel dropped it as soon as it got to the fruit beyond the seed layer of the part it started eating first. It hasn't touched any of the others. It will eat some millet if I put it in, but doesn't get particularly excited about it. It seems most interested in bread, which is the only food it has even considered coming close to me to get. I've been giving it a mix of pellets and seeds in its food bowl, sometimes with a treat ball thrown in, sometimes not. I haven't been offering veggies the last two or three days because I need to make a trip to the grocery store... Any recommendations for what I could get that would be most enticing? I've only offered bread twice.
I've done plenty of observing, I don't think I'm capable of ignoring the cockatiel 100%! It seems to be marginally more relaxed the past two days. I'll start with behavior until now and then say what's improved/changed.
Until yesterday its crest has almost always been straight up. That only changed when it would flatten it aggressively and flutter all over in a screaming panic when we had to reach in to change bowls, clean the cage, or handle it. Two days ago we moved it into a proper birdcage with doors for the bowls and a tray, so I don't need to reach inside anymore. When I would walk by, even if it wasn't very close, it would usually shuffle to the far end of the cage from me. Sometimes my walking by would send it into a panic and it would instead go flapping and screaming to the other end of the cage. Once there it often did a slight swaying motion. It frequently made itself skinny when people were around. It seemed to always be trembling, but I supposed that could be breathing? I haven't been able to find any solid answers on that so far. It does seem to like eating when I eat, which I think is promising. One thing I haven't been able to find much info on is a weird repetitive motion it would do for several minutes at a time. It would take a step towards the wall, put a foot on it, turn around on the perch, take a step away from the wall, and repeat over and over. It hasn't done that at all in the new cage though.
As of yesterday, the cockatiel is opting to hiss at me when I walk by instead of getting as far away as it can. I have also caught it with its crest in a slightly more relaxed position a couple times (still mostly up, but not maxed out), but it goes straight back up a moment later when it realizes I'm glancing from across the room. It has panicked once, but that's it. It is starting to show some interest in its surroundings, mostly the window and the tv. I caught it craning its neck all around to get a good view of the tv when I spied on it through my phone's camera earlier today, and it spends a good deal of time looking out the window. It chirps sometimes when I am not in the room. It stands by its food bowl 98% of the time and pretty much only moves to get to its water.
I have been hanging out in the same room a lot, which seems to be helping. I'm not entirely sure how to go about the gradually moving closer thing though. In that context, does relaxed mean "comfortable" or "not on red alert"? I have yet to see it ever get comfortably relaxed, but it does leave red alert state now.
Wolf, I am not offended at all. Personalized and detailed advice like you gave is exactly what I need right now.

I have a good deal of experience with chickens, and while I reckon that helps to some small extent, this is my first "pet" bird and they are extremely different. Beyond that, all I've done is hold friendly birds on a handful of occasions years ago, which also doesn't mean much of anything.
Here's a photo of it from today:
Not the best, but I don't have much else and I didn't want to freak it out by lingering to get a better shot.
Sorry this is so long! I wanted to include as many details as I could so you all could get the best impression of the situation I could give you. Thanks so much for your thoughts!