1) like any living language, French is full of slang, fad-words and trendy phrases, and new/loan words & expressions that have either not been ruled on by the Academie, or exist and are used in spite of Academic attempts to suppress them. These things are constantly changing, so I have no doubt that someone who learned his French from grandma may well sound quaint & old-fashioned to young folk who know all the up-to-date lingo.
This, exactly. Husband is Belgian, came to the US with his parents when he was very young. Some of the words he uses are considered to be out of date, they're not commonly used anymore. (There's also a bit of a dialect issue when he speaks to French speakers from France, but that's a completely different problem!) Linguistically, learning your language in a closed environment like this is referred to as "home (language)", ie home French, where your language isn't influenced by the society around you that speaks it. It stagnates and becomes a product of the era of the people you learned it from. I'm guessing this is maybe not *quite* as big of an issue in Western countries these days, with the advent of the internet and how you can do things like subscribe to cable packages with channels from your native country. That would keep you more in the current linguistic loop, so to speak.