Not usually. Sympathy cards are usually sent to people you know. Simply signing your name inside should let them know who it's from.
Just put his name. Ex: Joe, I'm sorry to hear about... My Sympathies, Sally Sue
My condolences, my sympathies...
It is etiquette to put the wife's name first and inside the card put her name first and then the husbands (the deceased was his mother-in-law) so he should be included.
Top left corner, opposite the stamp (top right corner).
Top left corner, opposite the stamp (top right corner).
Imagine your friend is standin in fornt of you, what would you say to him/her then? - put that on the card.
A return address is used in case the envelope is not delivered.
yes
Just the one whose parent it was. Unless their spouse was extremely close to their inlaw.
on the little lines on the back of the card.
You put it in the top left corner.