Firstly, Deep freeze does not suffer -35% damage. The base damage gets lowered by 20%, then the mastery increase lose 15%. This means that assuming no mastery from gear;
627074 damage.
at 10 extra mastery from gear (which is propably closer to the truth);
648476 damage.
Secondly, for ice lance, changes are cumulative, not additive (I hope I got that right way around).
Assuming 0 extra mastery;
797015 damage
and at 10 extra mastery;
811506 damage
Frostfire bolt should always be fired with FoF, os there you are correct. Ignite damage is proportional to the ffb damage, and since we can assume the mage in question to be crit soft capped, it is simpliest to say ignite loses 15% as well, losing 22121 damage. This brings the grand total to 3863469, or 97.8% of the original. Obviously, the higher your mastery, the less you will lose from this, and at a certain point in your mastery (ahich will be quite high, though) this will turn out to be a buff.
Do also note that elemental damage is not present and as such the actual percentage change will be even lower. That, and a deep freeze of 0 damage... if he actually hit with that thing, the difference would, again, be even lower.
These results are based on a single sample anyway. Simcraft simulations so far show this as an dps increase across the board. I suggest you continue following the topic at
http://elitistjerks.com/f75/t110339-..._cataclysm/p2/
They actually know their math there.