It's a protected green left turn arrow, right? How long does it stay green? How long does it stay orange? How long after it goes red does the light for oncoming traffic go green?

Regardless of your answers, I find it hard to believe that it turns orange within the time that the van enters the intersection and when you get past the stop line. If it turns orange before you get to the stop line, then, yes, you are supposed to stop. But that would mean it stays green for all of 1-2 seconds. I've never seen a light with such a short green cycle. Is that the case here? If so, you have to wait. If the light won't trigger for you, then treat it like a stop sign and proceed when there is gap.

If you do get into the intersection while the light is still green, are you saying you cannot complete the turn during the orange cycle? But you should at least be perpendicular to the flow of oncoming traffic by the time it turns green for them, and so you should be out of the blind spot behind the van. Just keep on pedaling!