I'm guessing what they're implying with Liam is that he is afraid that individually they are not stronger than the enemy. Kyle was stronger than Liam and Kyle died, but if Kyle died because his strength alone wasn't enough and Liam couldn't beat Kyle, then Liam also can't beat the enemy, so in...
I took it to mean "Shy" the persona is dead, as in who Teru is currently, and that she'll need to become someone else to use her power again. She'll need to become "Shine" or some other name.
I don't know if Kfufu could survive without Ameterasu's power - these are all children that died, presumably they're the one keeping their spirits going to an extent
Remember, it's the opposing team who have said that Aria is acting as Volante, not Aria. As far as I can see Volante's also make attacking runs which Haru is incapable of - this may lead to the opposing team thinking she's going to make a run as a Volante and then her throwing them off with just...
In a professional male game, passes are about 30mph. But this a youth girls game, so maybe 10-20mph at most?
Fastest a human has ever ran a 100m, average speed was 27mph. So she'd be going 1/3rd-2/3rds as fast as that? Doesn't seem too infeasible, definitely exceptional but that's kinda the point.