Unlike some languages, nouns after a number other than 1 are plural in English - even after 0 and 0.5.
The distinction between student results and students' results is a different question. Both are valid, and in most contexts there is no practical difference in meaning (though there could be in some cases). The first is a compound noun phrase, with ...
It is the noun for the verb, but it is not often used because of the other meaning of sewer (a pipe for used water and human waste), although the pronunciations are different.
For a factory worker, I would suggest sewing machine operator.
This is precisely meaning 3 in the Oxford Learners':
(also used as an exclamation) used to tell somebody that an action, a suggestion or a decision is acceptable
‘Bob wants to know if he can come too.’ ‘That's fine by me.’
"Fine by me" is a phrase that simply means "I think that's acceptable".