Storm would do more than stalemate him if she were an elemental. She has taken him out a couple of times with just her lightning in canon without ascending to her "perfect" form:
Most recently was in Jonathan Hickman's New Avengers #9:
So she zapped him on one occasion when he was being mind controlled by someone with an actual brain (read: Not someone with ice/snow instead of a nervous system which would be damaged by lightning), who doesn't know how to use Bobby's powers like he does. This would cause a mental backlash through Bobby and free him of that control, instantly KO-ing him, but not in such a way that it's applicable to an actual fight between him and Storm.
And your other one is from back in the day before Iceman was anywhere near the level of power he is today. Notice when knocked unconscious, he reverts to normal, whereas these days he's pure ice through and through. Saying that's applicable is like saying because some bullets nearly killed Wolverine back in the day, they could do so today too... Well, I suppose since he doesn't HAVE his healing factor anymore, they COULD, but you know what I mean.
Your first paragraph is speculative. There is no indication from panel that he was hurt from the mental backlash and not the lightning itself. In fact if he were somehow not vulnerable to such an attack, it doesn't matter how or who possessed him it still wouldn't affect him.
The second panel though it happened years ago does demonstrate he can be affected adversely by her lightning which is again demonstrated by the Hickman's showing. Yes he has progressed in his use of power, but he can still be affected and hurt when in his ice form.