I was waiting for Puffer Fishes to show up in a deck. Smart use of Unstoppable, more decks need that nowadays.
As Scaredgirl says, having Congeals usually works out better than Ice Lance, as Congeal holds more early-game power. By the time Ice Lance starts killing tougher creatures like FFQ, you've entered the phase of the game where you need to already be ahead in damage through poison. Although, Ice Lance does have the advantage of killing Mind Flayers outright, one of this deck's bigger worries.
One concern is that your creatures are pretty fragile and few in number... not sure if there's a real way to get around that though. Early Lobotomizer will ruin you as well; again, not much you can really do without having to pull in another element.
I'd actually say that while you indeed should not play the Ice Shield early game, this is a momentum deck so once you get going with several Unstoppables you might as well play it, as poison decks need to slow the opponent as much as they can while they build up poison counters, and even if it's stolen, no real harm is done.
I do have to question whether this will be fast enough at getting poison counters out early-game, the time where poison has to gain an advantage, because unlike Chysaoras, Puffer Fish are stopped cold by Sundial, giving your opponent time to get his own creatures and spells out. Again, not really sure if there's really any way around that with the current element balance...