Yellow chevron markings at end of runway, what do they mean?
Those are not chevrons but arrowheads used to mark the start of the runway. So, yes, he did land on the taxiway. 



Source: FAA Airfield Standards Quick Reference

He does land slightly before the runway threshold. He even says he is going to land short. Since there was nothing on the taxiway leading to the runway then it seems there is no problem doing that. 



screenshot from Google maps of KYKM runway 22 threshold

For comparison, chevrons mark either stopways or blast pads and look like this:


same source as first image

They may include an EMAS bed, so touching down there would not be a good idea.