Your plan is called "hidden city" ticketing.

Airlines have a lot of money to pay a lot of data miners to ferret out people who make a practice of hidden city or back to back ticketing. When such a person is identified, and you have been so identified, the airlines pay lots of money to lots of lawyers to send demand letters with an itemized list of the lost revenue and, perhaps, an offer to settle for a portion of that lost revenue.

You could go to court and fight their demand. Or, you could pay the offered settlement amount.

If you go to court and fight, you would have to hire a lawyer to defend yourself. The airline already has lawyers on their payroll who do this kind of thing all the time, routinely. Your cost for a lawyer could run into thousands of dollars and negate the savings you have accrued on airfare.

The airlines have all kinds of other ways to deal with you, besides getting a court judgement against you. They can, for example, ban you from their flights.

You are skating on thin ice, in my opinion. I suggest that you consider taking Amtrak both ways, in the future. Find something productive to do on the train.

You might also put "hidden city" and "revenue protection" in the search field of this message board and read what others have to say.