George, how disappointed you must be! To set such a stone in a less-than-perfect mounting is cringe-worthy, for sure. Reading your story makes me especially sad because I know that with a little time David can always find a "perfect" diamond, especially something like a radiant yellow – even a large radiant yellow. And, most likely, you do not need to wait as long as 8 months to see one or more viable stone(s) secured by David. Such a shame for EVERYONE that, apparently, all your options were not understood when you met with David. If it is out there, he can find it.
Regardless, once it was done, if you were not happy with the custom setting your jeweler made, certainly, you communicated this to your jeweler! I fear that since you took matters into your own hands, literally (tinkering with the setting, you were lucky to avoid total disaster), you now have no recourse with your jeweler at all.