First of all, yes, it refers to his wife.
As for the first part of the sentence, he intended to express the magnitude of his joy (My own happiness in the past often approached such joy that). The remaining part of it simply lays emphasis on his statement, as well as implies that his joy was the reason why he put his feelings down in words. (So as to unleash these feelings)
In my view, it is not strange. Maybe it is only strange for you because you have not come across such sentences.
Student or Learner