Here are my very naive answers to two of the original questions:

(2) I have never heard "talk their fill" *or* "take their fill", but I have heard (like most of us) "cry my fill", which suggests to me that " my fill" has long since broken away from its metaphorical connection with "eat my fill" and can mean "as much as one wanted to" with any verb, including "talk". They were so in love that no amount of conversation seemed enough -- why not?

(3) If I were in my winding sheet, I might very plausibly say I was on my way to the grave.