I am flying RT to Seattle in July and have a question I hope someone can answer for me.

I am halfway between Denver and Oklahoma City. The tickets from OKC to SEA are about $70 less than DEN to SEA, however, the OKC to SEA trip connects in DEN.

Can I buy a OKC to SEA ticket and "miss" my OKC to DEN connecting flight and just hop on in Denver?

Here are a few reasons I'm wanting to try this:
It's a NS flight from DEN to SEA.
I'd have less "air time" which would save me time on my trip.
I have a FFM credit card that would allow me to get two FREE RT tix from DEN to SEA for 18,000. It's a "zone" redemption, so if I were to redeem from OKC to SEA I'd have to use 25,000 for one ticket.

There are four of us going, so I'd like to buy two tickets from OKC to SEA and just get on in DEN while the other two tix I'd get FREE from DEN to OKC using my FFM credit card.

Is this possible to do? Thank you in advance for your responses!