Rather than PRN can you switch to part-time? At least that way you might have it easier dealing with the mandatory OT. Also, try going out of the box, can you work a weekend day? One night and a day? Sometimes you just have to start asking the right questions. Finally, if you can tough it out for another six months, you will probably have more options. The cold hard facts:
-You don't have floor experience, so that will be a tough transition, which isn't something that sounds good for you right now.
-OR nurses are expensive to train. Get to your two full years, get your CNOR, and you'll be able to get a PRN gig somewhere. Look at the back of the AORN journal, there are a lot of openings for OR nurses, hospitals just do not want to pay to train them. Often, there are jobs that are not advertised, but a unit will jump on an experienced OR nurse. I know mine would!
-You'll have more leverage if you tough it out. 1.5 years isn't a lot in OR nurse years. Two years is better.
Your hospital is short sighted, they'd be better off keeping you in some capacity. You're trained, you know where everything is, you know your surgeons, and frankly, they haven't gotten their money's worth yet. Usually it takes three years to recoup training costs. Not to mention, if you're a good employee (which I am sure you are) whydo they want to gamble on someone new? Look for another gig, then if you find one, go to your manager and state your case. If they're smart, they'll realize better to keep you in some capacity than lose you to a hospital that did not pay to train you.
Best of luck!