Just wait. They don't answer emails. If you leave the country before you get your DTV you run the risk of it being denied because you are no longer in the country. You can not change any detail after you apply.
It is no problem having your bank account in a different country. The big difference is how long it takes when applying in Vietnam as opposed to Canada. Thousands of people apply in Vietnam. It can be considerably faster applying in Canada.
For classes 6 months, or less, many have been given METVs instead. The multi-entry tourist visa valid for 6 months. More than 6 months of paid for classes are now the norm.