Nothing you can do about it. You lose the money and would need to apply again. A lesson in making sure the information you supply matches that on the passport
You can't cancel the DTV you already have and you can't hold 2 visas simultaneously. You should be able to convert a DTV to another visa type at an immigration office inside Thailand but that would very much depend on your prospective employer being able to satisfy the requirements for a Non-B visa inside Thailand, most want you to leave Thailand to obtain the Non-B as the paperwork is considerably less, but that won't work in your situation
Anonymous participant I understand you had the 500k but normally if it is a joint account you are expected to show double the money as half of the funds in the account is recognised as belonging to each account holder, one account holder doesn't own all of the funds. I was surprised they allowed it. As to your application you just need to supply your details, your husbands DTV details, your marriage certificate and a sponsorship letter saying your husband is responsible for you financially. Assuming your applying at the same consulate you can just supply the same information as previously, it would be odd for them not to accept it.
I'm surprised your husband was approved without having double the required money in a joint account. Nevertheless he should be able to right a sponsor letter for you as his wife