It depends on where and which class you will teach. Normally, you need a degree to apply for a visa, but it can also be waived in some cases. There are loads of dancing school here, many of them are successful too.
Would a strong Cv and testimonies help towards getting a permit as a teacher?
It won't have an impact on the visa decision from the immigration, because it's your employer who will issue the letter of request (in theory, requesting you as a teacher). but it will have an impact on decision of your future employer for giving you a job of course.
you have to show the letter from the bank insisting that you have this money once you apply for a visa, to prove that you can support yourself or your family while staying in Thailand.
As long as you have 400,000 baht in your account without withdrawing at all for 2 months. It is ok. It is very important that you don’t withdraw it to be less than 400,000 baht because the book bank is checked too.