Because both you and your wife's jobs appear to be exempt, your former employer was legally free to require both of you to work as many hours as he wanted you to work, without additional compensation to either of you. (Unless of course your employment contracts specifically prohibited this - more on this in a bit.)
Regarding business-related mileage, insurance and vehicle maintenance costs, employers in Colorado are not legally required to reimburse their employees for these. However, your former employer may be obliged to reimburse these if this was agreed-upon in your written employment contracts. (Again, more on this in a bit.)
The only cause of action I see in your post is regarding you and your wife's final pay. If I'm correct in understanding that neither of you received this, you both should file wage claims with either your state or the federal DOL.
Finally (this is the "in a bit" part), if your employment contracts clearly either limited you and your wife's daily and weekly working hours, or stated clearly that you would receive extra compensation for working hours above the amount of X, then you need to have an attorney review said contracts in full. If the attorney believes that your former employer violated the contracts, you may have a cause of action to sue your former employer in civil court for breach of contract.
This goes for the mileage, insurance and vehicle maintenance costs too. If your contracts clearly state that your former employer would reimburse you for some/all of these expenses, then you need to have an attorney review said contracts in full. If the attorney believes that your former employer violated the contracts, you may have a cause of action to sue your former employer in civil court for breach of contract.