If you were having petit dejeuner in France, you would be having breakfast. But you wouldn't be having an Anglo saxon cooked breakfast, you'd be having coffee and bread, butter, and jam.
où est mon déjeuner,
To say "sad little boy" in French, you would write "petit garçon triste."
un [petit] ami sincère ('petit' is used to confirm the romantic nature of the relationship - it is not likely that the boyfriend would use 'petit' in presence of his girlfriend)
Il est petit.
petit enfant
The idea of having a national gun is strange; there is no national gun in France and most French would laugh -or balk- at that idea.
Roland Petit was born on January 13, 1924 and died on July 10, 2011. Roland Petit would have been 87 years old at the time of death or 91 years old today.
Petit fours may be found in small chocolate or cookie or cake shops around your area. Costco has petit fours as well. You could also order them from Fannie May website.
it would be petit chien blanc
Lucien Petit-Breton was born on October 18, 1882 and died on December 20, 1917. Lucien Petit-Breton would have been 35 years old at the time of death or 132 years old today.
Because of the très modifier, it would be correct to phrase it either way. I think that your first option (un très petit dauphin) sounds more natural.
If you mean garçon, it would translate to "I love [...] small boy"