do you really believe people who learn Thai Cooking or Muay Thai are doing it to become professional chefs or One Championship pro fighters? Come on. Most are doing it for fun, and for the visa.
I'd advise you try one last time with a reputable agent offering some serious 'guarantees' of success (or money back). It's definitely worth the few extra thousand baht despite what some here keep saying. Of course, it's another visa fee to pay for, but at least you'll then be absolutely certain you'll have done everything you possibly could to get this DTV.
Maybe you can just pay a visit to the school if you don't believe what most of us share in this group? You seem to have done some research already and came up with good reviews everywhere, and you're still being cautious. What else can be said, online, that you'd accept to trust?