There’s two separate practices: Abstinence, and fasting, with some different rules. Abstaining means no sex as you said, and you don’t eat meat, with the exception of fish and mollusks (can’t remember if other types of seafood are allowed because I don’t eat seafood in general), and abstinence. From 14-17 you’re only required to do abstinence, even on Ash Wednesday and Good Friday. Abstinence is required on those days and every Friday of Lent. Fasting is only required on Ash Wednesday and Good Friday. I guess it’s kinda funny to imagine a couple marrying on a Friday and not being able to consummate.

And I think the confusion you’re talking about might be because the rules are very different in different countries (though I’m not sure about it varying by diocese as you suggest, it’s fairly consistent throughout countries). For example, where I live, there’s never been that rule to abstain on every Friday of the year, and I think it’s also like that in most places in Latin America. I’m pretty sure that Catholics in the US used to all abstain on Fridays even after 1983. I know that a lot of Tradcaths still do it, but they’re such a small minority (but very prevalent online ofc).

I’m sure you already knew a lot of that but the point is that afaik in Latin America we haven’t had as many inconsistencies with that because we keep abstinence and fasting to Lent only. Also, I hadn’t heard of fasting in Holy Saturday, that sounds like something regional as well.