I'm no freeze mage expert, but I think you possibly struggle in the early game? typically freeze mage is running 2x doomsayers to compensate, and as a board clear with frostnova..
I haven't seen this molten giant mage in the meta for 2-3 seasons now, but it seems like you may benefit from doomsayer//Archmage antonidas, ice lance 2x, pyroblast, and lastly but most niche would be malygos..
I think to make these fit.. Dropping Polymorph2x, mountain giant 2x healbot 1x.. cone of cold is also an iffy card in the deck.. it seems like this might seem too greedy also with Rag/boom/and archmage antonidas, so possibly cut one of them as well.
I also just noticed youre not running iceblock//barrier 2x.. i feel these would be essential cards to make laying down moltens a threat for your opponent..
a fun deck archetype to play though, I've been interested in building and playing some freeze mage lately.
goodluck on the ladder.