The word plutocracy means a government or society ruled by the rich.
There is no one-word substitute in English for "son-in-law."
The word you want is florist.
Sportsmanship is a word substitute for spirit of game
The word metalworking is one word.
eat, use
The word that works is idiot.
One possible substitute for "their" is "his" or "her" depending on the gender of the person/people being referred to. Another substitute can be "its" when referring to a non-human object or entity.
Elevate
A walker is a pedestrian.
Traditionalist
Omnipresent
Deaf