What are the steps and requirements for applying for a DTV visa in Bali while studying Muay Thai?

On the 29th of April I will with my family fly from

Phuket to Bali and apply for the DTV under the soft power Muay Thai.

I found a Muay Thai gym here after a recommendation from someone in this group 🙏🏽

They will provide me the correct paperwork for a 6 month course (1x a week, so enough time to keep training at our regularly gym).

I do have a few questions, that I not seem to find the answer to when I use the search feature. So hopefully someone will be kind enough to help answer them 🙏🏽:

1. What date should be put in the invitation letter, would this be the date that I want to start the course?

The gym asked me to give them the correct date for the letter.

2. I will apply online to the Jakarta embassy, would I say this to the gym for the letter as well or does the embassy in Jakarta have a specific name?

3. How do I get the passport stamp in Bali when entering?

I was there a few weeks ago, but we went through the electronic checkpoint, so no stamp was issued.

4. I don’t work at the moment, but I get enough benefits per month from my home country and extra every 3 months, would that be an issue (not working)?

I plan on getting back to work online once we get settled, I do have over 500.000 thb in funds, so that won’t be an issue.

5. When I get the DTV approved and apply for my kids as dependents, would the costs also be 10.000 thb each for them?

Can’t seem to find anything about that.