The shield blocks 400 damage regardless of magic resistance.
The 30% Magic Resistance is calculated everytime,as it is passive.
So, for the Fingers of Death Example :
If you dont have the shield activated, it will deal -30% damage.
If you do, it will still dealing -30% damage, and the rest of the damage will be used to
lower your "shield" ammount of Magic Block.
Lion's ultimate info can be found here
Level 1 : 500 Damage - 600 With Aghanim's
Level 2 : 650 Damage - 800 With Aghanim's
Level 3 : 850 Damage - 1025 With Aghanim's
So, 30% Magic Res. would lower the damages to:
Level 1 : 500 - 150 = 350 Damage Or 600 - 180 = 420 With Aghanim's
Level 2 : 650 - 195 = 455 Damage Or 800 - 240 = 560 With Aghanim's
Level 3 : 850 - 255 = 595 Damage Or 1025 - 307.5 = 717.5 With Aghanim's
So, ignoring any extra Magic Defense that the heroe may have, you would be able to completely ignore the ultimate's damage only if he is at Level 1, and without Aghanims.
Otherwise, you would take some extra damage.
Hope it Helps.
Source : Self tested @ Dota 2 with Friends.
As of now (29/04/2012), you can't. There is an external service who provides it, though.
It's this website: http://stats.dota2.be/. You have to create an account associated with your Steam account, so people won't be able to see others' individual stats. It seems they get their information from data mining every match played.
I'm not affiliated in any way with them, so I can't comment about security or anything. However, linking your Steam account is safe, as it uses the Steam API. In any case, I would recommend using a different password for this site.
Best Answer
There are three types of damage numbers shown: Strong physical attacks, strong spells and damage ticks. Both physical and magical attacks displays the "after calculation" values, but the damage ticks displays "before calculation" values. If I have missed any kind of damage, please post in comments so I can test it and add to this answer.
Strong physical attacks
When strong physical attacks are applied on a target, normally because of a Critical Strike happening, a damage is shown on the target of the damage. The number is the post calculation value, as proved by the following screenshot.
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Strong spells
When strong magical damage is applied on a target, specially Lion's and Lina's ult, a damage is shown on the target of the spell. The number is the post calculation value, as proved by the following screenshot.
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No donkeys were harmed in the making of this answer.
Damage ticks
Damage ticks are a whole different matter. There are spells like Venomancer's Poison Sting which deal damage per second or over time. For each damage tick, a damage number is shown on the affected hero. However, this number is before any calculation. If a hero is affected with a level 4 Poison Sting, "20" will be shown on the hero's head every damage tick. We can see that this is true by the next screenshot. Skeleton King has a 25% magic resistance. "20" is shown above his head. In the combat log, he received 15 damage.
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