The suggested translation would actually mean "The man draws a picture with a highlighter." While that can certainly be assumed, that's not what the sentence actually says. It mentions the act of drawing, not the product/picture.
Agree. My korean friend says 그림 can be omitted
The Korean sentence must end with a verb, so it's a sentence fragment, hence the English translation is a fragment. The sentence mentions the specific man (and his action) they are talking about.
Indeed, no verb here. It's a sentence fragment.
그림을 그리는 is a modifier to the noun (남자). The man that draws...
I agree. "그림" is not in the English gloss.
螢光펜으로 그림을 그리는 남자
this is not how it translates at all. the enlish for this should be "thd man who draws with a highlighter" or you could change the korean to "그남자는 형관펜으로 그림하다" or something like that