It was early December 2003, my first season as a Salvation Army bell ringer, when I was confronted with the question.

1 你关于同位语和非限制性定语从句的理解是正确的。

2 my first season as a Salvation Army bell ringer.

as在此是介词，意为”作为“，表示一个人的身份、职位等。通常其逻辑主语为人。要理解本句中as的这种用法，还需要准确理解物主代词作为限定词使用时的意义。生成语法认为，物主限定词表示所有关系时，表示的是一种逻辑主语关系，因此将这种用法的限定词称为subject determiner(主语限定词）。例如，my car=I have the car, my experiencce=I have the experience, my house=I own the house, my letter=I wrote the letter,etc.

因此，my first season as a Salvation Army bell ringer=I was spending the first season working as a Salvation Army bell ringer.或者It was the first season I worked as a Salvation Army bell ringer. 可以看出，在逻辑上my表示的是主语关系,相当于I作主语，as a...介词短语作状语，as介词短语的逻辑主语就是I，也即my。

我想这种解释可以回答网友的疑惑。