I wish I could hear what colloquial spoken Latin sounded like spoken by Romans, and whether the strict rules of grammar as taught at school were ignored as widely as they are in modern languages - I'm sure they must have been.

You might want to find a copy of WS Allen's Vox Latina – a Guide to the Pronunciation of Classical Latin.

I wonder if those very rules were imposed by the Roman Catholic church, rather than by native Romans? If you look at the plays by Plautus, you'll see a bunch of dialogue that is quite different from Cicero's speeches. The pronunciation of Latin in the Middle Ages pretty much followed how the local vernacular language was pronounced. In the 19th century, philologists and linguists started to reconstruct how Classical Latin might've sounded.

The history of Latin is rather long and interesting. I am currently reading a book on the Pompeii inscriptions. The grammar is all over the place from literary quotations to things like "Lucius got laid here". Also, as I mentioned other places, Romans used a hell of a lot of abbreviations. It was txting that brought down the Roman Empire.

Ceci n'est pas un seing.