Salaried Exempt? Maximum hours required to work?

My husband is a Quality Assurance Engineer for a company that creates software. When he was hired on six months ago, he asked about overtime in the interview and was told that it was not the norm. Since he hired on they have pushed him to work as many hours as possible, every day of the week.

Last week he told them he had plans and would not be able to work for Friday, Saturday or Sunday(Mother's day) - they acknowledged him and then called each day and demanded that he login from home and test the software they were creating. They also have called late at night after 10:30 pm and demanded he login to test the section of software they finished - which kept him working until 3am when he had to be up and out the door by 6am to meet with the client.

Yesterday the three managers working on his project came to him and demanded to know what hours he would be available for the next three weeks. When he asked them what they required they would not tell him, only that there is a deadline and everyone needs to put in the time to make it happen. They then followed up with an email asking him and other team members to email them back as to when they would work - they put themselves all down scheduled from 8am to "as late as it takes" for the next three weeks straight - no weekends off. He has talked to other employees who have been there over six months and they say that if you want to grow with the company you live at the company. Some were hired on to be leads but were passed over because for health reasons they could not work fifteen hours a day seven days a week.

My two questions are: 1) He writes test case scenarios for software and reports on his findings. Is he correctly classified as an exempt employee? 2) If he is exempt, how many hours and days can they require him to work with no time off? There is no compensation for his efforts and they are coming at great personal cost. Thanks in advance for any information.