That takes a while to read and I was skimming to that question mostly, but that was during the time when Birth by Sleep wasn't known to be a prequel, or at least people were referring it to be KH3. Doubtful that changes things, but there is a glimmer of hope that she'll do the song for KH 3(if it really will exist; the ending of 2 makes me think it could be finished chronologically) if disney decides to "pay" more.
If they offer her 110%(counting inflation) of what they payed her for KH2 I'd consider it if she was hurting. Since she's not, they need to offer 150%. If Utada's dad is asking more than this, then I would consider it a bit greedy, but who am I to know. Utada herself might just simply not want to do it. I wouldn't blame Utada for Disney being cheap. In a career you are always expected to get more money as time goes on even if a sequel isn't as successful(but of course KH3 would be up there even if it's worse than 2).