I understand that the Romans were unable to conquer Scotland so they build Hadrian’s Wall (which explains the survival of older cultures there). But as far as I know they occupied Wales and Cornwall, so how is it that the Celtic culture (language etc.) survived in those places?
Relevant detail: this changed a lot in 212.
Before that date, Roman citizenship basically implied Roman culture, language and lifestyle; but in that year Caracalla passed an edict granting citizenship to all free men in the Empire, so a lot of non-Latin-speaking locals were to be considered Roman citizens. (And taxed as such).
That said, I’d estimate the ratio of Latin speakers in the province to be 3~6% in the 4th century, based on a few Wikipedia numbers:
Not quite. The army was responsible for the enforcement of the rules, but the ones commanding the local elites and the army were former consuls appointed as governors.
I’m not sure at all. But I guess that, for both the slaves and the general working class, there was barely a difference. You still work to the bone, and die an ungrateful death, no matter if you’re doing it for the sake of a local tribal chief or for some “imperator” in the middle of nowhere.