What you describe sounds like an abuse of the ‘elder abuse’ law.
Surely it doesn’t cover such inconsequential things. But what do I know?
Well .. “... such inconsequential things”, lead to theft of credit cards .. so NO, tampering with your mail is not an inconsequential thing.
The fact the corner of an envelope was torn so the person could see inside the envelope - and the envelope appeared to have some sort of discernible card inside .. I’d say the chance of credit card theft was not just possible; the person delivering my mail was in effect attempting to steal from me.
And .. having worked at a residence for Seniors for over 6 years, stealing from Seniors is not a NEW thing; and you’d really be shocked to find out what people steal from seniors who can no longer care for themselves.