Is this sexual harrasment/sexual descrimination?

The description of the facts is a little vague - you were in a sexual relationship with him but then at some point you declined to sleep with him...

In Texas, an employer is free to have such a policy and hire only non-smokers. They may want to keep health-care costs down, reduce lost work time...

What is the maximum hours an exempt employee can work a week in the state of Texas

There is no maximum for an exempt employee, so in theory the maximum could be equal to the number of hours in a week.