The correct answer is sentence number 3 ("As a young man, he decided to become a doctor and pursue a life of healing and comforting").
In this paragraph we're introduced to Doctor Henderson, some of his good qualities, and the impact that his death has made in the community of Battle Creek, Michigan.
If we analyse the logical progression of the paragraph, sentence number 3 seems to be out of place. Talking about what his aspirations were as a young man, right after speaking of his death and before stating he will be remembered dearly, feels like an interruption in the flow of the paragraph and a deviation of the main theme which is the impact of his loss on the community.
Hope this helps!