Hi there,
I'm also a Canadian applicant who applied to UDM this year and was accepted. I was later on accepted by a Canadian school so I won't be attending UDM. However, I also have friends there and said many great things to me about UDM, so I think it's definitely a place worth going to study dentistry.
As for your stats, I would say you probably have more EC than I do based off of our description. I do have a higher GPA (3.93-3.95) and a slightly higher DAT score. I think reattempting DAT definitely is a good idea. Other than that, I would say really focus on your personal statement, make sure to give yourself sufficient time to write it, edit it and even ask your friends, family or other people to read it and give you suggestions. Once you receive your interview, I would say their interview is fairly laid back. The questions they ask you should be something you already have an answer to. Even if you didn't, just ask for a few moments to think about it then answer it. I had to do that for maybe 1-2 questions and that was fine for me. Don't take it super seriously, but make it more like an enjoyable conversation, really try to present yourself well during the interview time. Try to make yourself a likeable person and smile lots.
Other than that, my biggest advice would be to apply as early as you could. (I actually only got 1 interview invite this year which is from UDM. I think that may have been I finished my application a bit late. Everything was submitted to the schools in mid-Aug..)
Best of luck fellow Canadian friend!