Does ikke always come after the pronoun or can it be between the verb and the pronoun?
It should come after the pronoun. It could come between the verb and the pronoun, but then it would have a slightly different meaning, and it wouldn't be a complete sentence. It means you're emphasizing that it's "not us", but someone else.
"Jenta elsker ikke oss, men dem" = "She doesn't love us, but them"