Him playing around makes sense the first time he's translating the Spanish in the attic. It makes less sense when he keeps doing it after they're running for their lives from the Fratelli's, dodging booby traps and are facing yet another trap that is a full pipe organ made of human bones. And he's clearly scared when he translates it. But, maybe he just has weird defense mechanisms, I don't know.

Is your head cannon a front-loader?

Ish.

There's ye as in "hear ye, hear ye". That's a y. It's an inflected form of you, much as they had both thee and thou.

Then there's writing þe as ye.

It's called "thorn"

Eh, technically, if the word following 'the' starts with a vowel sound, you're supposed to say tge-with-a-long-e - the apple, the orange, the event, etc.