Okay, so this may be controversial but I do not agree with scaling Ryukyu's durability to 748 Megatons on the basis of Izuku's air pressure from his 100% strike on Tomura's head.
I bring this up is because Ryukyu was dead center from
Deku's 100% Wyoming Smash, which also produced a massive shockwave. Ryukyu didn't even move and wasn't bothered by this air pressure attack, despite her arms already being broken she held her ground. This air pressure attack should be much stronger than the 7-A+ rating when Deku could only use 8% without hurting himself.
From what I'm seeing, that version of 100% Deku upscales to
1 Gigaton for how badly he is damaging the
748+ Megatons Shigaraki.
The majority of the energy of his strike is going
into Tomura - not into the air pressure that is created as a byproduct of his attack. For the Ryukyu scaling to make sense here, about 252 Megatons of energy would be directly hitting Tomura and the excess 75% of the energy of his strike would be radiating outwards and hitting Ryukyu.
And it's not a case of Izuku producing 1 Gigaton of energy that goes into Tomura
and 748 Megatons of energy that goes into the air pressure that hit Ryukyu, because then his rating would be 1.748 Gigatons. That's not how it works.
Even if Izuku's 100% form in the War is stronger than his 100% form in the movie (and I have no problem with that), there is a difference in these feats. In the movie, the energy of Izuku's strike was directed upwards and had nothing to interrupt or absorb it which is why the full energy of his strike went up into the clouds. Here in the War arc, the majority of the energy of Izuku's strike was interrupted by Shigaraki's head. The excess air pressure let off by his attack has no scaleable value. We can't just point to other instances of air pressure he's created like in the movie and say "It must be as strong as this."
Not to mention this is ignoring other basic stuff like the fact that Ryukyu isn't tanking all of Izuku's air pressure. As big as she is, Ryukyu only has so much surface area and would only be being hit by a portion of the air pressure - just like how if an explosion went off next to her, she would only be tanking a certain amount of it - not the full value.