Isn't this just a Storm deck?
A bunch of cantrips. Check.
Pyromancer Ascension for long games. Check.
New piece Thing in the Ice. Check.
Wait...where are the rituals? Where is Goblin Electromancer? Hold the phone--where are the storm cards???
This is more than a new variant on an old deck. It's a complete reimagining of cantrip-heavy decks in Modern. Thing in the Ice is powerful enough to win the game by itself, and unless your opponent has a Path to Exile, then it's going to get in seven damage. At that point you can use Lightning Bolts and Lightning Helixes, especially when copied by Pyromancer Ascension, to finish the job. It's not as flashy, but it might be more effective.
Excepting the eighteen lands and the sixteen cards that combine to win the game, every card in the digs further into your deck. You are going to draw plenty of copies of your win conditions, so players hoping to overload your small threat base with answers are going to find themselves surprisingly outgunned.
Being able to chain spells almost ad infinitum also means that Thing in the Ice and Pyromancer Ascension are not nearly as slow as they read. Players assuming they have some time to answer or race them are going to find themselves the victims of their own naivety.
This deck is going to win plenty of games dealing exactly eighteen or twenty damage, so if your opponent gains a significant amount of life, things could get difficult. Fortunately, you have the extreme backup plan of using Thought Scour and Pyromancer Ascension to deck your opponent. It may not be recommended, but it's nice to have the option.
The white splash for Lightning Helix does more than add some much-needed lifegain to the deck. It gives you access to Path to Exile, Stony Silence, Wear // Tear, and Rest for the Weary in the sideboard, all very high-impact. Given your vulnerability to Leyline of Sanctity, I'm surprised there aren't more copies of Wear // Tear, but it's not a highly played card, so it's not a big deal.
I have one qualm with the deck as it is currently constructed. Sleight of Hand didn't make the cut and I have a set of gorgeous Portal Second Age copies that I have been dying to play. It's not better than any of the cards in the deck; it just sucks because they're really sweet.