My fiance is an EMT he works for a private ambulance company in Washington, DC but their main office is based in Maryland.
He remembers signing a form when he started working there that said he would sometimes be held over for up to an hour of his scheduled shift. Which by the way is 10 hours.
lately they have been told that they have a mandatory 2 hour hold over. he was also told that he would receive periodic pay raises and hasn't gotten a raise in three years.
is this hold over legal considering he signed on to accept a one hour hold over.

I am unclear on part of your question. For what you are describing as a "hold over", is payment being made for that time, and is that your question?
http://www.dol.gov/esa/whd/regs/compliance/whdfs22.pdf

Past that, there is no labor law requirement that raises ever be given (absent a MW wage increase pulling up a too law wage). Now an argument could made that the statements made by the employer regarding future raises rise to the level of an enforceable contract, but that is legally a tough argument to make, especially absent supporting documents. That is the sort of thing that you would probably have to take to a local attorney along with any documents. I just would not be very optimistic.

by holdover, I mean he signed a form saying that he may be required to work a up to an hour overtime. Now they are requiring last minute 2 hr mandatory hold overs.

I am not sure just what that is supposed to accomplish. Employers can generally require pretty much any employee to work pretty much any hours the employer wants. The employers do not need a signed form to do that. They can just tell the employee at the last minute.

you know I am reading the different post and threads and became curious, just what are the backgrounds of the people replying to these post. I mean are they really well versed in the labor laws or are they just giving opinions.

I can only speak for myself, but over 20 years as a payroll manager for a number of large national concerns, including wage and hour law compliance.

Most of the posters here are HR Professionals, Managers or the like. There aren't any specific qualifications to post here however. There are some lawyers but this is not the place to get legally binding attorney-client relationship type advice. If you want the advice of a lawyer well versed in employment law, you are going to have to pay for it. If you want an answer based on the experience of those who do this kind of thing for a living day in and day out, and you want it for free, you came to the right place.

Unless he has an enforceable contract that restricts the employer's ability to assign him more than one hour of OT, it is entirely legal to add more. Most offer letters presented at hire are not contracts but only a lawyer who has reviewed it in its entirety can tell you for sure.

As long as he is making at least minimum wage, there is no legal obligation to provide pay raises. Three years seems a long time to go without a raise but it isn't unheard of.