This is the place to post questions and discussions on usage and style. The members of the Wordwizard Clubhouse will also often be able to help you to formulate that difficult letter.
Is this correct:
1) He lost his dog at the age of seven months. The poor puppy died of a rare canine disease.
Is it "correct"? I think it's correct but seven months old seems a little young to own a dog.
"I became interested in girls at the age of twelve."
...am I a normal boy or am I some creepy old man who fantasizes about preteens?
I think that to extract Trolley's alternative meanings from his examples, you'd have to be making a deliberate effort to misconstrue them. The context will usually be sufficiently obvious to enable you to disambiguate sentences like those without much difficulty.
End of topic.