Anonymous participant to use option 3 your spouse or child would already have to have a DTV visa...
If you are working remotely or have a business overseas providing you with income that is a possible route. Or if you sign up for something in Option 2 that could be possible.
But since your spouse is Thai they don't have DTV and you wouldn't be eligible under this category.
Regarding the money in the bank account - transactions in and out are irrelevant. The length of time reauired to have a Bank account balance of over 500k baht varies depending on which embassy you apply through. Some require current balance only while others require up to 6 months.
Extremely common to apply for the DTV in other countries than your home or residency. Many people do this daily at various locations.
Each embassy has slightly different requirements, process, processing times and cost. Search this group for more info on the many posts about this.
Commonly used locations are Jakarta, Taipei, Vietnam. I got mine in Taipei. Flew there, applied in person the next morning, had it completed the following day and returned to Thailand.
Anonymous participant 0 baht to open account is quite rare because the banks basically "require" to purchase an insurance policy. Without the Thai account you end up paying transfer fees or ATM fees and then you will end up paying more than the agent anyway. Plus the time of going to dozens on bank locations is worth something unless you have nothing else to do.
When I opened mine a few months ago, the bank insurance was included in the agent fees. So the difference between trying to do it myself over many days or getting it done in less than 2 hours was only 3500 baht. I preferred spending those several days I saved to do other things