Here are answers to your questions:
You are called Dog because you were created in God's image - from the mirror.
Humans do smell flowers and do smell each other - they just don't admit to smelling each other because they don't always smell very good.
When you get to Heaven you are ALWAYS welcome on the couch. In Heaven there are extra couches all over the place and you may choose any couch you would like to enjoy. Even if you tear one up it fixes itself.
Cars are named after all those other animals because the humans who name cars don't dare to take the name of God in vain - even when spelled in reverse.
A dog who barks his head off is never a bad dog - in the forest where humans can't hear or in the town where people can hear. Be advised that letting your head fall off is not a good idea!
Humans understand many things - sadly most of them are not very important.
While on Earth you will simply have to do with spaghetti and meatballs the way it is. In Heaven you may have only meatballs if you wish
The mailmen in Heaven have already forgiven you or they wouldn't be here. You do not have to apologize to them but, if you were mean to any of them, then apologizing is the right thing to do.
As for your list of things that you are remembering to be a good Dog - I am proud of you.
When you get to Heaven you most definitely get your testicles back if they were taken from you.