Things are getting tighter so you really need to sign up for a course that's a minimum of 6 months, preferably a bit longer. 6 weeks of dental treatment can be done under a visa exempt entry, they're not going to give you a DTV based on that
It's very difficult to open a bank account on a DTV although not impossible. All you can do is go from branch to branch of every bank and hope you find one that will. You'll also need a residence certificate from immigration
You'll need the money to sign up for at least 6 months of your chosen soft power activity before applying. I'd save the support from your family in case they ask how you will support yourself over the 5 year duration of the visa