You have the option to go to Taipei before the 27th as they accept walk-ins up to that date and their processing time is short. You may need some days though, if you are 1 main applicant and wish to add spouse and child to the main applicants DTV.
it varies among the different embassies. Some request 3 month bank statements, some 6 month. Some requier that the amount has been there the whole time while others accept if the balance is over 500k thb on the day of application.
then I'm sorry to say that you are unlikely to get your visa approved in time for your departure. The processing time for many african nationalities are months, rather than weeks. Why did you apply so late/buy flight tickets before checking the visa procedures? 🤔
What John writes is true and there have been posts about this earlier. Unfotunately there is nothing you can do at this point, but to re-apply (the application is cancelled so your fee is lost).
If your wife is going to apply as your spouse/dependant you need to apply and get approved first. After that she can apply as your spouse (information from your aporoved DTV is needed to fill in her application).
you are correct in the beginning of your comment, but you've got the last part wrong. The visa is valid 6 month from the date it was issued (not 6 month from when he entered Thailand). The dates are clearly stated on the visa, in the OP's case it is valid until March 29.