" which is why you see the infinitive in this case. It is a future conditional construction. If "say" was not there, you would be correct in your assessment, but that was not the intention of this phrase as written.
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jooneyQ1) Do I have a correct assessment of the sentence structure?Yes.
jooneyQ2) How should I go about interpreting the meaning of "He selected a teenager to receive the money."? He selected a teenager so that(in order that) he/she could receive the money. Is this what it means?Yes. That seems reasonable.