If you are writing British English - I believe all are correct. Maybe a Brit can help.
American English - airplane
British people know what a fishmonger is - but my guess (unofficial) is that 95% of American have no idea what a fish monger is (of course, that is unless they are fans of British cooking shows.)
They are correct. But rather than `optical shop` try using optician. Also `The fishmonger is weighing` is correct but a little ambiguous. You would usually always finish the sentence to explain what he is weighing.