Hi and welcome to JA. Ray here to help you tonight.
You may consider an EEOC complaint.There may be age discrimination involved.Often this is a smokescreen for the real reason they are trying to force you out here and replace you with a younger and cheaper person.
An EEOC complaint about these issues would protect you from being an at will employee.If they continue to harass you here you would then file again claiming retaliation.Once you receive a right to sue letter you would be able to sue for damages for all the harm here.
It is unlawful to harass a person because of his or her age.
Harassment can include, for example, offensive remarks about a person's age. Although the law doesn't prohibit simple teasing, offhand comments, or isolated incidents that aren't very serious, harassment is illegal when it is so frequent orsevere that it creates a hostile or offensive work environment or when it results in an adverse employment decision (such as the victim being fired or demoted).
The harasser can be the victim's supervisor, a supervisor in another area, a co-worker, or someone who is not an employee of the employer, such as a client or customer.
I appreciate the chance to help you and am sorry you have had to deal with all of this.You have remedies here through EEOC and a civil suit as well.