One DR friend in the barrio--who possesses horrible diction and style--often asks me to rephrase what I say due to my word choice.
If your friend didn't understand you, was, because what you said was not understandable to anyone. He politely let you know that by asking your to rephrase what you said.
People on the DR are exposed to others Spanish speaking countries lingo, since all the popular "Telenovelas", movies and shows from Mexico, Colombia, Venezuela, Peru and even as far south as Argentina are aired in the DR and have become very popular.
You can ask any Dominican in the DR about a popular show, movies or Telenovelas in Mexico or Colombia and more than likely that person watch that show too.
Once, I had a Cuban translate my Spanish for someone in Guatemala. The Guatemalan thought that I was from Brazil.
Here you are contradicting yourself! You said that you learned proper, precise Spanish in high school and in college and now you are saying that a Cuban had to explained a Guatemalan what you were saying!!!!!! As I live here in the U.S. I see this everyday. English Speakers think because they had taken Spanish classes in high school and in college they are fluent in Spanish, but the reality is they are not fluent at all.
I haven't met an American that can speak Spanish because he learned it in the American public school system or in an American college. Only those that spent years studying Spanish in a Spanish speaking country are fluent in Spanish, and don't have problem understanding any accent in Spanish. The American I know that are fluent in Spanish had studied either in Spain or Chile.