It was jolly close.
I think your position was OK. By that, I mean it's where I would have been, so it must be OK.
Looks like the sort of thing one would shrug off had it not been for the junction. As he'd stopped, it seems fair to mention it to him.
You were diplomatic, polite and clear when you spoke.
Others may disagree with me, but a stronger position would probably have availed you nothing. His speed and trajectory appear to have been selected without thought for you. You might just have made yourself closer to the danger.