How to proceed when graduate advisor treats me terribly, possibly because of age?
Don't walk. Run.

Your advisor's behavior is unfair, disrespectful, abusive, and deeply unprofessional.  Their behavior reflects horribly on the department, and since it's unlikely that you are the only victim, may undermine the value of your degree.

The moment the professor blew up at you for using another textbook, it would have been appropriate for you to walk out of his office/classroom without another word, drop the class, report his behavior  (both in writing and in person) to the department head, and find (and/or demand) a new thesis advisor.  Even now, I would recommend all of those responses.

If the department has your back, break all contact with your old advisor, finish the degree, and get out.  Block his phone number (but save his voice mails).  Reroute his emails to a separate folder (but don't delete them).  If he shows up at your office, ask him to leave; if he refuses, leave yourself; if he follows you, walk to the department chair's office.  In any case, document everything.

If the the department is unwilling or unable to help you separate from your abusive advisor and finish your degree, then the department is being abusive and unprofessional.  Again, since you are unlikely to be the only victim of this abuse, it will get out, and it will undermine the value of your degree.  Then your best choice is to leave the degree program, apply elsewhere, and try to transfer as much credit and research progress as possible.

I recommend contacting the associate professor who left to act as a potential reference, and for more general advice about how to proceed.  She knows the local political landscape far better than any random stranger on the internet.

Your age and educational background is not relevant here.  Your advisor's behavior is completely unacceptable, and you should not have to put up with it for even a second longer.  Get. Out. Now.