not a lawyer either but I know you're in a southern state so it's unlikely you have state laws that are favorable to employees.
1. as jordan said, as long as an employer pays you for the time at time-and-a-half it's legal. They have to provide breaks as well. even if they tried to make you or got you to sign a contract saying you'd take less, I think they can be prosecuted for failing to pay the time-and-a-half because it is their job to uphold those Wage and Labor laws, not your job to know what they are and refuse to sign the contract.
2. Given that they're asking you to sign something, it seems like legal ass covering just to make sure they don't even have to think about the hint of a lawsuit. It's also a way to threaten your asses by reminding you who's boss. And, it's also a way to get psychological buy in. 10 days into it, if someone gets sick of the ridiculous hours, they'll be less like to whine or call in sick because they remembered they 'voluntarily' signed a contract.
You can call the Dept of Labor and they are actually very helpful on the phone about a lot of this stuff. I'm sure they can tell you for sure, without having to get an attorney to know. E.g., they explained to me that I was screwed b/c I was the only employee, thus labor laws didn't apply to me. Everyone else was family or a contractor, so I was SOL.