You retain the amount of health that you had right before receiving the "killing" blow and get healed for about 334 HP, depending on your health, you have to iceblock before the first or second tick.

You seem to misunderstand the mechanics. Absolute corruption reduces healing received by 99%. Nothing but 3 groups of paladins can heal through this. Spiritlink totem does not heal you, it changes your HP. The high HP of the other players in range gets distributed to you. If they get some healing, you get some HP.
As to the best usage of Iceblock: There is nothing I can say about, I just tried Absolute Corruption for a Normal Mode kill last lockout, for fun basically. A more experienced and progressed mage than me has to step in to give an answer.

As for Cho'gall HC, I use my Ice Block for the first Unleashed Shadows AoE, right after I get Corruption: Absolute at 100 Corruption, because I found out that IB removes Corruption: Malformation, which applies to everyone after 75 Corruption.
I give healers less pain doing this, and also when the deflection bug worked for tanks with glyphed Grounding Totems, my tentacles did not randomly destroy Grounding Totems this way.

I was reading about the PoM trick today that Arcane mages use at the beginning of a fight to get the Arcane Potency buff before the pull, and PoM would be off cooldown shortly after to make use of it again. It got me to thinking of other things I could do at the start of a fight as Arcane to improve the opening burst sequence. Most people pre-pot with the 1200 int volcanic potions for a 25 second spell power boost which also increase our mana pool size. If we pre-potted a couple seconds earlier and then ate our mage food to fill up our 12k larger mana pool before the pull, would this not allow us to make better use of Mana Adept, as well as have a slightly longer burst phase?

It seems to me this would be a theoretical damage increase over the course of a fight. The only loss I can see is that you would have to take your potion a few seconds earlier, so you would potentially have the int buff for about 3 seconds less then you normally would from pre-potting. Does anyone know if this would be a worthwhile damage increase? or am I just overcomplicating the start of the fight for an insignificant change?

As a fire mage, at what level of haste is it considered optimal to make changes to the standard rotation? For example, if we experience a 0.9-second cast time on Fireball, is that far enough below the 1-second GCD floor to merit hard-casting Pyroblast instead? Likewise, at what point is it best to leave Living Bomb out of the rotation?

Edit: Another interesting study would be to determine at similar levels of gear and extreme levels of haste (eg. Sinestra) the point at which the fire spec becomes preferable to arcane in single-target situations.

I believe this would be as simple as recording your exact cast time (say, 0.92s for Fireball), multiplying its Simcrafted DPET*0.92 (to account for the lost time under the hard GCD cap), and comparing to the DPET of the direct damage portion of a hard-cast Pyroblast, plus the appropriate DPET of Pyroblast DoT ticks. The DoT portion might be low due to the constant DoT refreshing (3.0s minus haste modifiers) versus quick cast time (sub-2s). The Pyro DoT might only be allowed to tick during LB refreshes (also questionably useful, as they're sub-GCD with extreme haste too) or other instants.

Edit: Sorry if that wasn't definitive; I'll do some math and hopefully get back to you soon.

Note that due to the new nature of DoTs in cataclysm, the pyro dot will continue to tick, even if constantly refreshed. Your point isn't invalid, but the DoT damage isn't reduced by it being refreshed.

I've read the compendium and there says I've to use the Flame Orb to regenerate mana because the high rate of AM procs, but I'm asking my self after reading some WoL and notice the majority of Arcane Mages are using it in the opening of the fight and on cooldown, my question is, is this real worth to use on cooldown for a dps gain?

Use it conditionally. For a stand and nuke fight, use Flame Orb on CD for extra damage. However some fights call for small burst periods, or other reasons why your mana might drop. In these scenarios, if your Flame Orb CD is about ready, you might as well use it to get you from 70% mana back to 95% quicker than you otherwise would be able to.

Example of times when you drop below 95% mana during a non-burn phase and a Flame Orb can help you out:
Ignacious shield - you want to land a few 4stack AB's on him.
Rohash storm shield - " "
Periods of sustained burst, regardless of Evoc cooldown. For example Nefarion achievement: you are probably going to do a full burn, Evocate, then a full burn again. Now you've completed the 50% landing, but you're oom and 1:30 from an Evocate. Flame Orb can help you get some mana back.

Yes. Flame Orb has the highest DPET of any of our spells (highest DPM as well, possibly), so it's worth using every time it's off of its cooldown.

Yes, they undid the 6sec-cooldown-change (in build 14179).