I am not sure about these "facts". Why would quebec accent stay the same for centuries? Languages are unstable, especially their pronunciation. Consider also the extraordinary diversity of accents in uk. Did only one cross the Atlantic?
Believe it or not, there is an entire field called linguistics that studies human language and how it evolves.
In terms of lexicon, much of the archaic flavour is actually the result of 19th-century language reformers trying to restore old words. In the meantime, Icelandic had borrowed heavily from Danish.
Indeed, there is the field of linguistics, and scholarly treatments of Icelandic (as opposed to pop-sci presentations of the language as a time capsule like yours) point out that Icelandic has undergone a great deal of innovation like any other North Germanic language.