He looked after them ever <since> <after> he moved there.

[Marika33]

Note though that I do consider it okay to use 'since' with a past time endpoint in certain contexts—most notably in past perfect sentences.

OK, I can understand using "since" with the past perfect, "On the 27th of July 2019, he smoked again. It was the first time he'd done it since 2008", but sometimes I feel like it's unnecessary to write/say such long sentences/lines. Instead, I would prefer the past simple option, "On the 27th of July 2019, he smoked for the first time since 2008", but only if it is grammatical.

For myself:
I refused to go to church ever since I was 12.
I refused to go to church after I turned twelve/from the age of twelve.
But:
I have refused to go to church ever since I was 12. (until now)
I had refused to go to church ever since I was 12. (needs another point in the past to connect the past perfect with)