In an effort to reduce costs, my boss has reduced my hours. I was hired in as full-time salaried. I am now working 32 hours (still considered full time i guess). Can he do this even though I was hired in at a weekly salary?

Also, he has not reduced any one elses hours. I know this because I handle payroll and see everyones weekly hours.

Do I have a case to keep my orginal pay rate?

Is there a cba or employment contract that states your hours cannot be reduced? If not then yes your employer can do this

As long as the employer is not reducing hours based on protected characteristics (age, race, religion, national origin, gender etc), its perfectly legal unless there is a CBA.

It makes sense for an employer to determine which position's hours can be cut and which one's cant for business necessity.

The employer could also reduce your salary to no less than $455 per week and, all other things being equal, you would still be exempt. Have you been changed to being paid hourly?

He did not say...beginning with payroll entered this week (work last week), I entered myself as hourly.
The owner is very good at playing dumb and saying that he did not do or say things he did, and refuses to put anything in writing.

He also has refused to pay bonuses to people (they do have an employment contact) claiming that he does not know anything about it, and refuses to give me or anyone else the time to explain it

Sounds like you need to dust of your resume

At some point the best cure to a bad employer is to find another employer.