mistrusting or untrusting
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
"Everyone" is one word.
The word metalworking is one word.
An apostrophe means one of two things - either you're leaving out some letters (like can't means cannot or doesn't means does not) or you are indicating possession. If you put an apostrophe after the word suspects, you get suspects' which means "belonging to the suspects." An example sentence would be something along the lines of "The suspects' belongings are at the police desk."
eat, use
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.
The word that works is idiot.
Elevate
Traditionalist
Omnipresent