I think you have nailed it (= understood perfectly).
It's interesting that you used two sentences in the Japanese translation. If you wanted to combine them, I think you could write:
...but is there any way to get the the first part (of my sentence above) inside the second part? (I am trying to get a better handle on Japanese complex sentences.)
Incidentally, I think you're right about the relationship between restrictive and non-restrictive clauses and the definite / indefinite article. In archaic English, the word "which" could be preceded by "the". The best example I could pull up quickly was this:
"Invoking then the Most Holy Name of Our Lord Jesus Christ, and of His most glorious Mother Mary, ever Virgin, for this Our definite sentence, the which ... we present in these writings, ..."
More information than you probably want to know about the word "which" can be found here:http://machaut.uchicago.edu/?action=search&resource=Webster%27s&word=Which&quicksearch=on
晋三さん, who won the lottery, is my uncle.
The 晋三さん who won the lottery is my uncle.
If you re-read above, you will find that these sentences mean slightly different things. It matters whether you put the commas in or not. It changes the meaning of the sentence.
If you are still confused after re-reading, let me know where you get lost and I'll try to explain more clearly.
The Elephant's Child