well if you want to play a numbers game 400, ill give a bit considering speed work. you said this:
Ex: Guy runs 22.0 for 200m. He goes out in 23.0 seconds and comes home in 25 seconds. That's a 48. 22×2 = 44. 48-44 = 4 seconds. That's what most collegiate 400m runners are capable of. Me, on the other hand run 23.91. I go out in 25, come home in 29/30. 24 x 2 = 48. 54-48 = 6 seconds. See the difference here? They can maintain their speed much better than I can, not just based off fitness, but specific endurance as well.
even with that 6 second defecit, should you increase your 200 time from 23.91 to 23.41 (which im sure you can do, just maybe not right now;) ) than you already cut off a whole second! how easily do you think youll be able to close from a 6 second defecit to a 4 second defecit? i think that will be MUCH harder. and something you can work on as your general fitness and specific fitness gets better.
and a side note: i dont think your 'fitness' is necesarily holding you back. youve mentioned overtraining previously in this thread and in another thread. focus on recovery and relax about your races. earlier this season i was a serious headcase cuz i couldnt match my best times. but it was all mental, injury related, and i just forgot how to run my race. youve been working hard, and i know you can get sub 54 if you just prepare yourself properly mentally and physically. i think you mentioned your PR was 54.12. youre so close! just reach out and grab it.