1. You check your email aggressively during your time off.
2. You think that 50 hours a week is normal.
3. You think 1/8 weeks of _unpaid_ on-call is reasonable.
How many sev-2s and sev-3s do you get during your one week on-call? If more than 10/week, can you think about how many are outside of business hours?
2) I think 40-50 is acceptable, I would ask you to find anywhere salaried that 40 is the true upper limit - I'm telling you I can't remember a week I spent more than 50 - 40 is definitely the norm though.
3) I get paid for my time in the office, work outside of the office is highly unusual for my on-call rotation - it happens maybe once or twice a year as I noted.
Far less than ten - almost none outside business hours. Last time I was paged outside of business hours it was because someone messed up who they paged :)
I'd suggest that you're on a lucky on-call rotation, and seem to have a good manager!
If I were still there, I'd say get on VPN, head over to tt.amazon.com and see the stats of other teams' on-call rotations, and estimate how many of their pages are outside business hours ;)
But instead you get services built where dozens of pages a week is the norm.