My last job was a salary position, exempt from overtime pay. But I was often required to work 18-20 hours per day with anywhere from 3-6 hours between the time I left the office and the time I was required to return. In addition, I had an hour long commute to and from work.
When my health began to deteriorate, I went to my employer and told him I could no longer work these extended hours. So he fired me.
I have now been offered the same job, with a different company. I am certain I will be expected to work 60-100 hours per week, yet I will be offered a set salary.
Are there any laws protecting exempt/salaried employees from having to work extreme hours or not being allowed sufficient time between shifts?

Unfortunately, no, unless you work in certain job classifications such as a truck driver.

Let me know if you have any other questions.

I would like to take some kind of action to voice my opinion and protest the labor laws concerning salaried emplyees. I don't believe it should be legal to require a salaried emplyee to work 20+ hour days, six days a week, with only a few hours between shifts. Who should I write to concerning this issue?

You may want to start with your local representatives or even your senator.

Good luck and let me know if you have any other questions.