How to max out size? Even with "Cartoonish" enabled, it stops at "Titanic" before she wakes up?
It should set to cartoonish if you enabled it. You'll see when she wakes up. Ivan's mom is also cartoonish, so to make sure it worked you can check on her.
Ivan's mom has the Cartoonish sprite, but the text says Titanic. Is it supposed to just be visual, rather than also descriptive?
(Also, is there any benefit to the different foods for Evee?)
Yeah it's just visual. There isn't a benefit to the different foods, that mechanic didn't make it in.