You can book a slot online, but needs to be booked well in advance. So, I've never done that βΊοΈ Google Bangkok immigration and you should be able to find their website. Sorry, I don't have it from the top of my head.
I went there today for my 90 day report, arrived just after 8.30 and was out after 2 and a half hours. Just enjoy the little food market they have and have some breakfast, makes the waiting a lot more bearable.
Search for my report of my application in HCMC, I was in similar situation and included a cover letter explaining the situation and included the signed contract of the job which was still to start. I was approved.
You booked a 1-week trip to apply for the DTV? Vietnam gives a 90-day tourist e-visa. I can only wonder why you this to yourself. The application takes 5-10 working days. If they ask for further documents, the clock resets to 5-10 working days. You should have planned accordingly.
That is not nonsense, it's nothing but your opinion. One of the categories of the DTV is about Thai culture. Thai food definitely falls under that. Might be problematic for extension but let's just live and let live.