The sentence makes sense in terms of syntax. But think about the word "consider". It does not sound great to say that an "assumption" "considers". Normally, a person "considers". Perhaps one of these words may be better : "include" "consist of" "encompass".

yes, that's fine. a fuller version would be 'the assumptions that were made considered three factors"

This is tricky for me without more context. I would invite more discussion on this. "Considered" is a verbal modifying three factors. Made is used by the nominative which is "the assumptions." I would say yes, but a provisionally qualified answer.